Help me with Ubuntu Linux, Fixing errors, troubleshooting

When i try to download for instance from a ppa, in the middle of running the command i get this error: Err:19 [login to view URL] bionic Release 404 Not Found [IP: [login to view URL] 80] and later on in the same run of the command this can be seen: Reading package lists... Done W: Target Sources (main/source/Sources) is configured multiple times in /etc/apt/[login to view URL] and /etc/apt/[login to view URL] W: Target Sources (main/source/Sources) is configured multiple times in /etc/apt/[login to view URL] and /etc/apt/[login to view URL] W: Target Sources (main/source/Sources) is configured multiple times in /etc/apt/[login to view URL] and /etc/apt/[login to view URL] W: Target Sources (main/source/Sources) is configured multiple times in /etc/apt/[login to view URL] and /etc/apt/[login to view URL] W: Target Sources (main/source/Sources) is configured multiple times in /etc/apt/[login to view URL] and /etc/apt/[login to view URL] W: Skipping acquire of configured file 'main/source/Sources' as repository '[login to view URL] bionic InRelease' does not seem to provide it ([login to view URL] entry misspelt?) E: The repository '[login to view URL] 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. W: Target Sources (main/source/Sources) is configured multiple times in /etc/apt/[login to view URL] and /etc/apt/[login to view URL] W: Target Sources (main/source/Sources) is configured multiple times in /etc/apt/[login to view URL] and /etc/apt/[login to view URL] W: Target Sources (main/source/Sources) is configured multiple times in /etc/apt/[login to view URL] and /etc/apt/[login to view URL] W: Target Sources (main/source/Sources) is configured multiple times in /etc/apt/[login to view URL] and /etc/apt/[login to view URL] W: Target Sources (main/source/Sources) is configured multiple times in /etc/apt/[login to view URL] and /etc/apt/[login to view URL] Also, from time to time Ubuntu freezes on me and i have to reboot from my power switch. If you would find a fix for that i would be really glad The first problem is my main concern at the moment, as i cant download/install almost anything from the terminal at the moment, and its hurting my work.