diff --git a/backend/server/adventures/serializers.py b/backend/server/adventures/serializers.py
index ce543894..129758c9 100644
--- a/backend/server/adventures/serializers.py
+++ b/backend/server/adventures/serializers.py
@@ -2,8 +2,10 @@
 import os
 from .models import Adventure, AdventureImage, ChecklistItem, Collection, Note, Transportation, Checklist, Visit, Category
 from rest_framework import serializers
+from main.utils import CustomModelSerializer
 
-class AdventureImageSerializer(serializers.ModelSerializer):
+
+class AdventureImageSerializer(CustomModelSerializer):
     class Meta:
         model = AdventureImage
         fields = ['id', 'image', 'adventure']
@@ -19,11 +21,12 @@ def to_representation(self, instance):
             representation['image'] = f"{public_url}/media/{instance.image.name}"
         return representation
     
-class CategorySerializer(serializers.ModelSerializer):
+class CategorySerializer(CustomModelSerializer):
+    num_adventures = serializers.SerializerMethodField()
     class Meta:
         model = Category
-        fields = ['id', 'name', 'display_name', 'icon', 'user_id']
-        read_only_fields = ['id', 'user_id']
+        fields = ['id', 'name', 'display_name', 'icon', 'user_id', 'num_adventures']
+        read_only_fields = ['id', 'user_id', 'num_adventures']
 
     def validate_name(self, value):
         if Category.objects.filter(name=value).exists():
@@ -31,14 +34,17 @@ def validate_name(self, value):
     
         return value
     
-class VisitSerializer(serializers.ModelSerializer):
+    def get_num_adventures(self, obj):
+        return Adventure.objects.filter(category=obj, user_id=obj.user_id).count()
+    
+class VisitSerializer(CustomModelSerializer):
 
     class Meta:
         model = Visit
         fields = ['id', 'start_date', 'end_date', 'notes']
         read_only_fields = ['id']
                                    
-class AdventureSerializer(serializers.ModelSerializer):
+class AdventureSerializer(CustomModelSerializer):
     images = AdventureImageSerializer(many=True, read_only=True)
     visits = VisitSerializer(many=True, read_only=False)
     category = CategorySerializer(read_only=True)
@@ -102,7 +108,7 @@ def update(self, instance, validated_data):
         
         return instance
     
-class TransportationSerializer(serializers.ModelSerializer):
+class TransportationSerializer(CustomModelSerializer):
 
     class Meta:
         model = Transportation
@@ -113,7 +119,7 @@ class Meta:
         ]
         read_only_fields = ['id', 'created_at', 'updated_at', 'user_id']
 
-class NoteSerializer(serializers.ModelSerializer):
+class NoteSerializer(CustomModelSerializer):
 
     class Meta:
         model = Note
@@ -123,7 +129,7 @@ class Meta:
         ]
         read_only_fields = ['id', 'created_at', 'updated_at', 'user_id']
     
-class ChecklistItemSerializer(serializers.ModelSerializer):
+class ChecklistItemSerializer(CustomModelSerializer):
         class Meta:
             model = ChecklistItem
             fields = [
@@ -131,7 +137,7 @@ class Meta:
             ]
             read_only_fields = ['id', 'created_at', 'updated_at', 'user_id', 'checklist']
   
-class ChecklistSerializer(serializers.ModelSerializer):
+class ChecklistSerializer(CustomModelSerializer):
     items = ChecklistItemSerializer(many=True, source='checklistitem_set')
     class Meta:
         model = Checklist
@@ -194,7 +200,7 @@ def validate(self, data):
 
         return data
 
-class CollectionSerializer(serializers.ModelSerializer):
+class CollectionSerializer(CustomModelSerializer):
     adventures = AdventureSerializer(many=True, read_only=True, source='adventure_set')
     transportations = TransportationSerializer(many=True, read_only=True, source='transportation_set')
     notes = NoteSerializer(many=True, read_only=True, source='note_set')
diff --git a/backend/server/main/utils.py b/backend/server/main/utils.py
new file mode 100644
index 00000000..0963ba62
--- /dev/null
+++ b/backend/server/main/utils.py
@@ -0,0 +1,10 @@
+from rest_framework import serializers
+
+def get_user_uuid(user):
+    return str(user.uuid)
+
+class CustomModelSerializer(serializers.ModelSerializer):
+    def to_representation(self, instance):
+        representation = super().to_representation(instance)
+        representation['user_id'] = get_user_uuid(instance.user_id)
+        return representation
\ No newline at end of file
diff --git a/backend/server/users/serializers.py b/backend/server/users/serializers.py
index 63b5b7dc..776bb78e 100644
--- a/backend/server/users/serializers.py
+++ b/backend/server/users/serializers.py
@@ -196,6 +196,7 @@ def to_representation(self, instance):
             # remove any  ' from the url
             public_url = public_url.replace("'", "")
             representation['profile_pic'] = f"{public_url}/media/{instance.profile_pic.name}"
+        del representation['pk'] # remove the pk field from the response
         return representation
 
 class MyPasswordResetSerializer(PasswordResetSerializer):
diff --git a/backend/server/worldtravel/serializers.py b/backend/server/worldtravel/serializers.py
index 386f673a..0f2ed734 100644
--- a/backend/server/worldtravel/serializers.py
+++ b/backend/server/worldtravel/serializers.py
@@ -1,6 +1,8 @@
 import os
 from .models import Country, Region, VisitedRegion
 from rest_framework import serializers
+from main.utils import CustomModelSerializer
+
 
 class CountrySerializer(serializers.ModelSerializer):
     def get_public_url(self, obj):
@@ -36,7 +38,7 @@ class Meta:
         fields = '__all__'
         read_only_fields = ['id', 'name', 'country', 'longitude', 'latitude']
 
-class VisitedRegionSerializer(serializers.ModelSerializer):
+class VisitedRegionSerializer(CustomModelSerializer):
     longitude = serializers.DecimalField(source='region.longitude', max_digits=9, decimal_places=6, read_only=True)
     latitude = serializers.DecimalField(source='region.latitude', max_digits=9, decimal_places=6, read_only=True)
     name = serializers.CharField(source='region.name', read_only=True)
diff --git a/frontend/src/lib/components/AdventureCard.svelte b/frontend/src/lib/components/AdventureCard.svelte
index 519d9761..c8f0de35 100644
--- a/frontend/src/lib/components/AdventureCard.svelte
+++ b/frontend/src/lib/components/AdventureCard.svelte
@@ -167,7 +167,7 @@
 		<div class="card-actions justify-end mt-2">
 			<!-- action options dropdown -->
 			{#if type != 'link'}
-				{#if adventure.user_id == user?.pk || (collection && user && collection.shared_with.includes(user.uuid))}
+				{#if adventure.user_id == user?.uuid || (collection && user && collection.shared_with.includes(user.uuid))}
 					<div class="dropdown dropdown-end">
 						<div tabindex="0" role="button" class="btn btn-neutral-200">
 							<DotsHorizontal class="w-6 h-6" />
@@ -188,7 +188,7 @@
 							</button>
 
 							<!-- remove from collection -->
-							{#if adventure.collection && user?.pk == adventure.user_id}
+							{#if adventure.collection && user?.uuid == adventure.user_id}
 								<button class="btn btn-neutral mb-2" on:click={removeFromCollection}
 									><LinkVariantRemove class="w-6 h-6" />{$t(
 										'adventures.remove_from_collection'
diff --git a/frontend/src/lib/components/AdventureModal.svelte b/frontend/src/lib/components/AdventureModal.svelte
index 4c77a998..332efcb3 100644
--- a/frontend/src/lib/components/AdventureModal.svelte
+++ b/frontend/src/lib/components/AdventureModal.svelte
@@ -52,7 +52,14 @@
 		location: null,
 		images: [],
 		user_id: null,
-		collection: collection?.id || null
+		collection: collection?.id || null,
+		category: {
+			id: '',
+			name: '',
+			display_name: '',
+			icon: '',
+			user_id: ''
+		}
 	};
 
 	export let adventureToEdit: Adventure | null = null;
@@ -73,7 +80,14 @@
 		user_id: adventureToEdit?.user_id || null,
 		collection: adventureToEdit?.collection || collection?.id || null,
 		visits: adventureToEdit?.visits || [],
-		is_visited: adventureToEdit?.is_visited || false
+		is_visited: adventureToEdit?.is_visited || false,
+		category: adventureToEdit?.category || {
+			id: '',
+			name: '',
+			display_name: '',
+			icon: '',
+			user_id: ''
+		}
 	};
 
 	let markers: Point[] = [];
diff --git a/frontend/src/lib/components/CategoryFilterDropdown.svelte b/frontend/src/lib/components/CategoryFilterDropdown.svelte
index 12a57267..d9069be6 100644
--- a/frontend/src/lib/components/CategoryFilterDropdown.svelte
+++ b/frontend/src/lib/components/CategoryFilterDropdown.svelte
@@ -53,7 +53,7 @@
 						on:change={() => toggleSelect(type.name)}
 						checked={types.indexOf(type.name) > -1}
 					/>
-					<span>{type.display_name + ' ' + type.icon}</span>
+					<span>{type.display_name + ' ' + type.icon + ` (${type.num_adventures})`}</span>
 				</label>
 			</li>
 		{/each}
diff --git a/frontend/src/lib/components/ChecklistCard.svelte b/frontend/src/lib/components/ChecklistCard.svelte
index 40741d18..c42c6e9b 100644
--- a/frontend/src/lib/components/ChecklistCard.svelte
+++ b/frontend/src/lib/components/ChecklistCard.svelte
@@ -56,7 +56,7 @@
 			<button class="btn btn-neutral-200 mb-2" on:click={editChecklist}>
 				<Launch class="w-6 h-6" />{$t('notes.open')}
 			</button>
-			{#if checklist.user_id == user?.pk || (collection && user && collection.shared_with.includes(user.uuid))}
+			{#if checklist.user_id == user?.uuid || (collection && user && collection.shared_with.includes(user.uuid))}
 				<button
 					id="delete_adventure"
 					data-umami-event="Delete Checklist"
diff --git a/frontend/src/lib/components/ChecklistModal.svelte b/frontend/src/lib/components/ChecklistModal.svelte
index 2e004154..cb0fa9dc 100644
--- a/frontend/src/lib/components/ChecklistModal.svelte
+++ b/frontend/src/lib/components/ChecklistModal.svelte
@@ -34,7 +34,7 @@
 				name: newItem,
 				is_checked: newStatus,
 				id: '',
-				user_id: 0,
+				user_id: '',
 				checklist: 0,
 				created_at: '',
 				updated_at: ''
@@ -135,7 +135,7 @@
 			<p class="font-semibold text-md mb-2">{$t('checklist.editing_checklist')} {initialName}</p>
 		{/if}
 
-		{#if (checklist && user?.pk == checklist?.user_id) || (user && collection && collection.shared_with.includes(user.uuid)) || !checklist}
+		{#if (checklist && user?.uuid == checklist?.user_id) || (user && collection && collection.shared_with.includes(user.uuid)) || !checklist}
 			<form on:submit|preventDefault>
 				<div class="form-control mb-2">
 					<label for="name">{$t('adventures.name')}</label>
diff --git a/frontend/src/lib/components/NewCollection.svelte b/frontend/src/lib/components/NewCollection.svelte
index 29887a7f..5ba50ba4 100644
--- a/frontend/src/lib/components/NewCollection.svelte
+++ b/frontend/src/lib/components/NewCollection.svelte
@@ -8,7 +8,7 @@
 	import Calendar from '~icons/mdi/calendar';
 
 	let newCollection: Collection = {
-		user_id: NaN,
+		user_id: '',
 		id: '',
 		name: '',
 		description: '',
diff --git a/frontend/src/lib/components/NoteCard.svelte b/frontend/src/lib/components/NoteCard.svelte
index 699dc0bd..44ea314e 100644
--- a/frontend/src/lib/components/NoteCard.svelte
+++ b/frontend/src/lib/components/NoteCard.svelte
@@ -59,7 +59,7 @@
 			<button class="btn btn-neutral-200 mb-2" on:click={editNote}>
 				<Launch class="w-6 h-6" />{$t('notes.open')}
 			</button>
-			{#if note.user_id == user?.pk || (collection && user && collection.shared_with.includes(user.uuid))}
+			{#if note.user_id == user?.uuid || (collection && user && collection.shared_with.includes(user.uuid))}
 				<button
 					id="delete_adventure"
 					data-umami-event="Delete Adventure"
diff --git a/frontend/src/lib/components/NoteModal.svelte b/frontend/src/lib/components/NoteModal.svelte
index b304dbea..af9648cf 100644
--- a/frontend/src/lib/components/NoteModal.svelte
+++ b/frontend/src/lib/components/NoteModal.svelte
@@ -113,7 +113,7 @@
 			<p class="font-semibold text-md mb-2">{$t('notes.editing_note')} {initialName}</p>
 		{/if}
 
-		{#if (note && user?.pk == note?.user_id) || (collection && user && collection.shared_with.includes(user.uuid)) || !note}
+		{#if (note && user?.uuid == note?.user_id) || (collection && user && collection.shared_with.includes(user.uuid)) || !note}
 			<form on:submit|preventDefault>
 				<div class="form-control mb-2">
 					<label for="name">{$t('adventures.name')}</label>
diff --git a/frontend/src/lib/components/TransportationCard.svelte b/frontend/src/lib/components/TransportationCard.svelte
index 767dc64e..20ee4336 100644
--- a/frontend/src/lib/components/TransportationCard.svelte
+++ b/frontend/src/lib/components/TransportationCard.svelte
@@ -59,7 +59,7 @@
 			{/if}
 		</div>
 
-		{#if transportation.user_id == user?.pk || (collection && user && collection.shared_with.includes(user.uuid))}
+		{#if transportation.user_id == user?.uuid || (collection && user && collection.shared_with.includes(user.uuid))}
 			<div class="card-actions justify-end">
 				<button on:click={deleteTransportation} class="btn btn-secondary"
 					><TrashCanOutline class="w-5 h-5 mr-1" /></button
diff --git a/frontend/src/lib/types.ts b/frontend/src/lib/types.ts
index 937c11a6..1a1f9745 100644
--- a/frontend/src/lib/types.ts
+++ b/frontend/src/lib/types.ts
@@ -13,7 +13,7 @@ export type User = {
 
 export type Adventure = {
 	id: string;
-	user_id: number | null;
+	user_id: string | null;
 	type: string;
 	name: string;
 	location?: string | null;
@@ -43,7 +43,7 @@ export type Adventure = {
 		name: string;
 		display_name: string;
 		icon: string;
-		user_id: number;
+		user_id: string;
 	};
 };
 
@@ -69,7 +69,7 @@ export type Region = {
 export type VisitedRegion = {
 	id: number;
 	region: number;
-	user_id: number;
+	user_id: string;
 	longitude: number;
 	latitude: number;
 	name: string;
@@ -87,7 +87,7 @@ export type Point = {
 
 export type Collection = {
 	id: string;
-	user_id: number;
+	user_id: string;
 	name: string;
 	description: string;
 	is_public: boolean;
@@ -122,7 +122,7 @@ export type OpenStreetMapPlace = {
 
 export type Transportation = {
 	id: string;
-	user_id: number;
+	user_id: string;
 	type: string;
 	name: string;
 	description: string | null;
@@ -141,7 +141,7 @@ export type Transportation = {
 
 export type Note = {
 	id: string;
-	user_id: number;
+	user_id: string;
 	name: string;
 	content: string | null;
 	links: string[] | null;
@@ -154,7 +154,7 @@ export type Note = {
 
 export type Checklist = {
 	id: string;
-	user_id: number;
+	user_id: string;
 	name: string;
 	items: ChecklistItem[];
 	date: string | null; // ISO 8601 date string
@@ -166,7 +166,7 @@ export type Checklist = {
 
 export type ChecklistItem = {
 	id: string;
-	user_id: number;
+	user_id: string;
 	name: string;
 	is_checked: boolean;
 	checklist: number;
@@ -193,5 +193,6 @@ export type Category = {
 	name: string;
 	display_name: string;
 	icon: string;
-	user_id: number;
+	user_id: string;
+	num_adventures: number;
 };
diff --git a/frontend/src/routes/adventures/+page.svelte b/frontend/src/routes/adventures/+page.svelte
index 03a1737f..948b7a6b 100644
--- a/frontend/src/routes/adventures/+page.svelte
+++ b/frontend/src/routes/adventures/+page.svelte
@@ -15,7 +15,6 @@
 	console.log(data);
 
 	let adventures: Adventure[] = data.props.adventures || [];
-	let categories: Category[] = data.props.categories || [];
 
 	let currentSort = {
 		order_by: '',
@@ -36,14 +35,13 @@
 	let typeString: string = '';
 
 	$: {
-		console.log(typeString);
-		if (typeof window !== 'undefined' && typeString) {
-			let url = new URL(window.location.href);
-			url.searchParams.set('types', typeString);
-			goto(url.toString(), { invalidateAll: true, replaceState: true });
-		} else if (typeof window !== 'undefined' && !typeString) {
+		if (typeof window !== 'undefined') {
 			let url = new URL(window.location.href);
-			url.searchParams.set('types', 'all');
+			if (typeString) {
+				url.searchParams.set('types', typeString);
+			} else {
+				url.searchParams.delete('types');
+			}
 			goto(url.toString(), { invalidateAll: true, replaceState: true });
 		}
 	}
diff --git a/frontend/src/routes/adventures/[id]/+page.svelte b/frontend/src/routes/adventures/[id]/+page.svelte
index fcf326b1..de1ed349 100644
--- a/frontend/src/routes/adventures/[id]/+page.svelte
+++ b/frontend/src/routes/adventures/[id]/+page.svelte
@@ -82,7 +82,7 @@
 {/if}
 
 {#if adventure}
-	{#if data.user && data.user.pk == adventure.user_id}
+	{#if data.user && data.user.uuid == adventure.user_id}
 		<div class="fixed bottom-4 right-4 z-[999]">
 			<button class="btn m-1 size-16 btn-primary" on:click={() => (isEditModalOpen = true)}
 				><ClipboardList class="w-8 h-8" /></button
diff --git a/frontend/src/routes/collections/[id]/+page.svelte b/frontend/src/routes/collections/[id]/+page.svelte
index ae379b19..b0a1cc63 100644
--- a/frontend/src/routes/collections/[id]/+page.svelte
+++ b/frontend/src/routes/collections/[id]/+page.svelte
@@ -263,7 +263,7 @@
 	</div>
 {/if}
 {#if collection}
-	{#if data.user && !collection.is_archived}
+	{#if data.user && data.user.uuid && (data.user.uuid == collection.user_id || collection.shared_with.includes(data.user.uuid)) && !collection.is_archived}
 		<div class="fixed bottom-4 right-4 z-[999]">
 			<div class="flex flex-row items-center justify-center gap-4">
 				<div class="dropdown dropdown-top dropdown-end">
@@ -275,7 +275,7 @@
 						tabindex="0"
 						class="dropdown-content z-[1] menu p-4 shadow bg-base-300 text-base-content rounded-box w-52 gap-4"
 					>
-						{#if collection.user_id === data.user.pk}
+						{#if collection.user_id === data.user.uuid}
 							<p class="text-center font-bold text-lg">{$t('adventures.link_new')}</p>
 							<button
 								class="btn btn-primary"
diff --git a/frontend/src/routes/search/+page.svelte b/frontend/src/routes/search/+page.svelte
index 20e6de1e..c131802e 100644
--- a/frontend/src/routes/search/+page.svelte
+++ b/frontend/src/routes/search/+page.svelte
@@ -41,13 +41,13 @@
 			publicAdventures = data.props.adventures;
 
 			if (data.user?.pk != null) {
-				myAdventures = myAdventures.filter((adventure) => adventure.user_id === data.user?.pk);
+				myAdventures = myAdventures.filter((adventure) => adventure.user_id === data.user?.uuid);
 			} else {
 				myAdventures = [];
 			}
 
 			publicAdventures = publicAdventures.filter(
-				(adventure) => adventure.user_id !== data.user?.pk
+				(adventure) => adventure.user_id !== data.user?.uuid
 			);
 
 			if (data.props.osmData) {