it seems you still didn't edit this file properly:
Code:
/etc/apt/sources.list.d/additional-repositories.list
it's a simple text file.
you have to make sure you have a "#" at the beginning of every line inside that file.
you can use nano, or any other text editor, but you have to do this with sudo (= root privileges).
after you have done that post the output of
Code:
cat /etc/apt/sources.list.d/additional-repositories.list
and
Code:
sudo apt-get update
