Q

$ git remote add origin git@github.com:lut/EvolutionApp.git
fatal: remote origin already exists.

$ git push -u origin master
fatal: '  ' does not appear to be a git repository
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

My keys were added succesfully

You've successfully authenticated, but GitHub does not provide shell access.

Solve

Try and redefine the ssh url for remote origin:

git remote set-url origin git@github.com:name/projectname.git

Only git remote set-url can change an existing remote URL (as opposed to git remote add, to add a new remote name and URL). Here, the issue was the URL of the existing remote ‘origin’, EvolutionApp: it needed to be replaced by a valid one. Using git config url.“ssh://git@github.com/”.insteadOf https://github.com/ would not have helped, considering there was no HTTPS URL in the first place.

Finally

After input

ssh -T git@github.com

Although it still output

You've successfully authenticated, but GitHub does not provide shell access.

It just a notice .