You have a local Git-Repository with a Remote-Repository which is a fork from somebody else's Repository.
Sync your fork with the original repository to get all the updates that happened there.
$ git remote add upstream https://URL-TO-ORIGINAL-REPO/ORIG-REPO.git
Typically you should have now two remotes: origin (fork) and upstream (original)
$ git fetch upstream
git checkout master
git merge upstream/master
git push