This is the output of apt-get update
I have no idea what is going on, but I cannot update anymore, any help would be appreciated.
Hit:1 http://security.ubuntu.com/ubuntu bionic-security InRelease
Hit:2 http://ca.archive.ubuntu.com/ubuntu bionic InRelease
Hit:3 http://ca.archive.ubuntu.com/ubuntu bionic-updates InRelease
Hit:4 http://ca.archive.ubuntu.com/ubuntu bionic-backports InRelease
Ign:5 http://ppa.launchpad.net/nilarimogard/webupd8/ubuntu bionic
InRelease
Err:6 http://ppa.launchpad.net/nilarimogard/webupd8/ubuntu bionic Release
404 Not Found [IP: 91.189.95.83 80]
Reading package lists... Done
E: The repository 'http://ppa.launchpad.net/nilarimogard/webupd8/ubuntu bionic Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.