Open the "Software & Updates" application. At the bottom, there's an "Installable from CD-ROM/DVD" section. Unlike the screenshot I'm sharing, you will have a selected option in that section.

Uncheck whatever is there.

You also have a customer repository added that uses a domain that doesn't resolve anywhere.

To fix that, in the same application you were in, go to the "Other Software" tab and search for an entry that mentions that retorque domain and uncheck it.

Close the application, and it will ask you to reload. Do that, and try updating your system again.