Sometimes a pull request/merge request needs changes before it can be merged. On GitHub, a typical workflow is like:

git switch -c feature main
git pull https://github.com/friend/repo.git main
# other person's repo branch PR/MR is from

Then one edits the files, and commits the changes. However, if the Git pull command fails like:

fatal: Not possible to fast-forward, aborting.

From the new feature branch:

git pull https://github.com/friend/repo.git main
git reset FETCH_HEAD --hard

Then one edits the files, and commits the changes.

Finally, the generic workflow to merge the PR/MR is:

git switch main
git merge --no-ff feature
git push