Adjusting main animation
Here is a video on how to do it, below is a text-based explanation:
In order to update the main page animation we would:
- Delete the old 
homepage.gifin thesrc/assets/imgfolder. - Upload a new 
homepage.gifinto thesrc/assets/imgfolder. 
Deleting the old animation
In order to delete the old homepage.gif, we would go the main
page. Direct into the src/assets/img folder.

Then we direct towards to the homepage.gif file.

We click the delete icon in the upper right corner.

We will be redirected to a page where we can fill out the following form.

- Enter an appropriate title e.g. 
Delete homepage animation - Make sure the 
Commit directly to the main branchis checked. - Click the 
Commit Changesbutton. 
Now the old animation is deleted.
Uploading a new animation
In order to upload a new animation we again go to the src/assets/img folder.

Now we are going to click Add File. This will open a dropdown menu in which we
are going to click Upload Files.

This will open a new page, where we can click the choose your files link to
open the file explorer and upload a homepage.gif.
IMPORTANT NOTE: make sure the file is actually called homepage.gif otherwise
it will not work

Then we again come to the Commit Changes section.

- Enter an appropriate title e.g. 
New homepage animation - Make sure the 
Commit directly to the main branchis checked. - Click the 
Commit Changesbutton. 
Note: The demo page may take a while to properly update after this. It may first fail to load the animation. After around 10 minutes this should be fixed however.