I want to reset to a specific commit. I use the command
git reset --hard Head~5
Updates were rejected because the tip of your current branch is behind
You can forcibly push but this is potentially problematic.
Are there other people working on this repo or is it just you? Are you absolutely sure you want to erase those commits from the remote?
git push -f origin branch-name will update the remote branch to match the changes you've just made.
But you need to take care when doing this. If you have colleagues working on the same branch you should tell them in case they have already pulled in those changes. Plus they may have pushed other changes which you'd be overriding.