Updates Warning

Solved the problem being inspired from this question. Basically, on line 43, I had deb http://archive.canonical.com/ubuntu hirsute partner multiverse and all I had to do was to erase multiverse becoming deb http://archive.canonical.com/ubuntu hirsute partner.

The reason why I had to remove multiverse is that http://archive.canonical.com/ubuntu is not a general-purpose repository as stated in the link provided.

Open Software & Updates and check these settings... you may have to select a different Download from...

Update #1:

Edit /etc/apt/sources.list...

and change:

deb http://archive.canonical.com/ubuntu hirsute partner multiverse

to this:

deb http://archive.canonical.com/ubuntu hirsute partner