Alright, let's start by setting up collections to store user activities. In Adalo, collections are like your data storage. So, here's what you do:

1. Head over to the database section of your Adalo app.
2. Create a new collection called "Users" (if you haven't already).
3. Now, create another collection named "Activities" with fields like User, Activity Description, Timestamp, and any other fields you think are important.

Next, we need to link the "Users" collection with the "Activities" collection.

1. In the "Activities" collection, add a relationship field that connects it to the "Users" collection. Make sure this relationship is set as "Many Activities to One User".

Now, let's log some user activities. For instance, if you want to log when a user creates a new post:

1. Go to the screen or form where the user action happens (like the post creation form).
2. Add an action to create a new record in the "Activities" collection.
3. In the action settings, link the User field to the logged-in user and set the Activity Description and Timestamp fields accordingly.

Time to design the interface where users can see their activity feed.

1. Add a list component to the screen where you want to show the activity feed.
2. Set the list to display data from the "Activities" collection.
3. Customize the list item to show relevant activity info, like Activity Description and Timestamp.

Let's make sure the feed shows the right data by filtering and sorting activities.

1. Open the list settings on the activity feed screen.
2. Add a filter to display only activities related to the current logged-in user.
3. Sort the list by Timestamp in descending order so the most recent activities show up first.

Finally, let's test the activity feed to make sure it logs and displays user activities correctly.

1. Perform different activities within the app, like creating posts or updating profile info.
2. Check the activity feed to see if these activities are logged and displayed accurately.

Make sure everything works as expected and tweak anything that needs fixing.