Error Log

Reading package lists... Done
W: The repository 'http://ppa.launchpad.net/webupd8team/y-ppa-manager/ubuntu cosmic Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: GPG error: http://ppa.launchpad.net/webupd8team/java/ubuntu trusty InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY C2518248EEA14886
W: The repository 'http://ppa.launchpad.net/webupd8team/java/ubuntu trusty InRelease' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: Failed to fetch http://ppa.launchpad.net/webupd8team/y-ppa-manager/ubuntu/dists/cosmic/main/binary-amd64/Packages  404  Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.