I think you can nix "As a teacher" and this will be just as clear.

General feedback--I'd suggest something like:
 "You can then do a code review within the pull request, giving line-by-line feedback. If you allow your students to submit corrections, they can push fixes up to their forks, which will be reflected in the pull request.

Since you don't want any solutions in the original assignment repository, you should leave the pull request unmerged. When you're finished giving feedback, you can close the pull request and leave a :+1: (`:1:`) in a final comment."