sudo apt-get update fails. Software and updates not opening either

I am using Ubuntu 16.04. The error I get is as follows: W: http://archive.canonical.com/dists/precise/Release.gpg: Signature by key 630239CC130E1A7FD81A27B140976EAF437D05B5 uses weak digest algorithm (SHA1) W: The repository ‘https://packagecloud.io/computology/apt-backport/ubuntu xenial 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…

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