How to push here?

I have a private project, I made my first push, it 's all ok, but after that I always receive this message/ What I have to do I change only one file and can’t push to my repo/

To gitlab.com:vitalyk/projectName
! [rejected] master -> master (non-fast-forward)
error: failed to push some refs to ‘git@gitlab.com:vitalyk/projectName’
hint: Updates were rejected because the tip of your current branch is behind
hint: its remote counterpart. Integrate the remote changes (e.g.
hint: ‘git pull …’) before pushing again.
hint: See the ‘Note about fast-forwards’ in ‘git push --help’ for details.

git push -f origin master

To gitlab.com:vitalyk/projectName
! [rejected] master -> master (non-fast-forward)
error: failed to push some refs to ‘git@gitlab.com:vitalyk/projectName’
hint: Updates were rejected because the tip of your current branch is behind
hint: its remote counterpart. Integrate the remote changes (e.g.
hint: ‘git pull …’) before pushing again.
hint: See the ‘Note about fast-forwards’ in ‘git push --help’ for details.

i never saw this message before not on GitHub or here