The issue is as per the the error messages: one of the Apt source list files is incorrect, preventing it from being read, and thus preventing Apt from updating.
You can either try fixing that file yourself (searching for the error message will return plenty of results), or post the contents
inside "[code]..[/code]" tags and someone can advise.
Also, in general you should be providing more information - just saying "debian" is not enough - there are multiple supported versions of Debian, and the precise version can be applicable. (If unsure as to what information is relevant, the output of "
inxi -b" is often a good start.)