Choosing Repositorie error

This is a known issue which (according to google) is already solved, https://crbug.com/952287

What happens if you try again?

Or - if that still fails - try the command

wget -q -O - https://dl.google.com/linux/linux_signing_key.pub | sudo apt-key add -

After trying your suggestion I reboot but didn’t work.

"didn't work" in what sense?
Error messages? If yes, please provide the full text - both of the command(s) that you executed and the response that you received!

The initial error come from the last time I had an Software Update and append other times before.
I went to Synaptic and change the Download From: to other server and on update the error comes
up this append with all the servers.

Could not download all repository indexes

The repository may no longer be available or could not be contacted because of network problems. If available an older version of the failed index will be used. Otherwise the repository will be ignored. Check your network connection and ensure the repository address in the preferences is correct.

An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://dl.google.com/linux/earth/deb stable Release: The following signatures were invalid: KEYEXPIRED 1555048520 KEYEXPIRED 1555048520 KEYEXPIRED 1555048520 KEYEXPIRED 1555048520The repository 'http://ubuntu.mirror.neology.co.za/ubuntu xenial Release' does not have a Release file.Data from such a repository can't be authenticated and is therefore potentially dangerous to use.See apt-secure(8) manpage for repository creation and user configuration details.The repository 'http://ubuntu.mirror.neology.co.za/ubuntu xenial-updates Release' does not have a Release file.Data from such a repository can't be authenticated and is therefore potentially dangerous to use.See apt-secure(8) manpage for repository creation and user configuration details.The repository 'http://ubuntu.mirror.neology.co.za/ubuntu xenial-backports Release' does not have a Release file.Data from such a repository can't be authenticated and is therefore potentially dangerous to use.See apt-secure(8) manpage for repository creation and user configuration details.The repository 'http://ubuntu.mirror.neology.co.za/ubuntu xenial-security Release' does not have a Release file.Data from such a repository can't be authenticated and is therefore potentially dangerous to use.See apt-secure(8) manpage for repository creation and user configuration details.Failed to fetch http://dl.google.com/linux/earth/deb/dists/stable/Release.gpg The following signatures were invalid: KEYEXPIRED 1555048520 KEYEXPIRED 1555048520 KEYEXPIRED 1555048520 KEYEXPIRED 1555048520Failed to fetch http://ubuntu.mirror.neology.co.za/ubuntu/dists/xenial/main/binary-amd64/Packages Cannot initiate the connection to ubuntu.mirror.neology.co.za:80 (2001:43e8:10:42::25). - connect (101: Network is unreachable) [IP: 2001:43e8:10:42::25 80]Failed to fetch http://ubuntu.mirror.neology.co.za/ubuntu/dists/xenial-updates/main/binary-amd64/Packages Cannot initiate the connection to ubuntu.mirror.neology.co.za:80 (2001:43e8:10:42::25). - connect (101: Network is unreachable) [IP: 2001:43e8:10:42::25 80]Failed to fetch http://ubuntu.mirror.neology.co.za/ubuntu/dists/xenial-backports/main/binary-amd64/Packages Cannot initiate the connection to ubuntu.mirror.neology.co.za:80 (2001:43e8:10:42::25). - connect (101: Network is unreachable) [IP: 2001:43e8:10:42::25 80]Failed to fetch http://ubuntu.mirror.neology.co.za/ubuntu/dists/xenial-security/main/binary-amd64/Packages Cannot initiate the connection to ubuntu.mirror.neology.co.za:80 (2001:43e8:10:42::25). - connect (101: Network is unreachable) [IP: 2001:43e8:10:42::25 80]Some index files failed to download. They have been ignored, or old ones used instead.

Thank you for trying to help

Thanks Manfred Hampl, that solved my question.