Somehow a file called
Untitled Document 1 was copied to the
/etc/sources.list.d folder. That's very odd. Such a file is usually a word processing document, and not a configuration file at all.
You can move this file to your desktop by opening a Terminal window (Ctrl+Alt+T) and running:
sudo mv /etc/apt/sources.list.d/Unt* ~/Desktop
Then the file will be on your desktop (in case it contains something important), and the first error message should go away. If it doesn't, please comment here and edit your question with details of what happened next.
The first message was actually a "warning"; it might work even if you leave
Untitled Document 1 in place,.
The second error message can be solved by following the instructions here: