This solution didn't worked for you:
The solution is to remove Medibuntu from your list of repositories:
◾Open a terminal
◾Type gksu gedit /etc/apt/sources.list to edit the list of repositories (replace “gedit” with “pluma” if you are running MATE, or with “kate” if you are running KDE)
◾Remove any line which contains “medibuntu” in it and save the file
◾Type apt update in the terminal
I think you ruined your setup by running commands and stuff which are given as a 2nd, 3th or 4th solution. Always try the "official" solution first!