Is it obligatory to file a lawsuit to claim one's right to exam grades, or to remain silent for fear of harming someone at the university, knowing that the course professor might teach the student again?

We advise you to consult experts in teaching and grading to guide you to the optimal course of action in your situation, and then pray Salatul-Istikhara (the prayer for guidance). If your heart feels at ease with the matter, it is a sign of good. Otherwise, proceed with what is easy for you to do, and you are permitted to repeat the Istikhara prayer.