Why I cannot push my code to github?

Question

$git push origin master
To git@github.com:dimitar9/first_app.git
 ! [rejected]        master -> master (non-fast-forward)
error: failed to push some refs to \'git         


        

Answer 1

This means that there are some changes on GitHub which have not been merged into your current branch. To resolve this, do what the error message is telling you to: git pull, resolve any conflicts, then try pushing again.