This question is easy to answer for once, because you are not allowed to work in Germany while staying in Germany with a language course visa. That means during your language course you are not a “real” student, because you are only preparing studies in Germany.
I would strongly recommend that you accept this restriction, because you’ll loose your right to stay in Germany if you don’t.
When you have got an admission to a German university you are a “full” student (after inscription) and that includes the permission to work in Germany, but still you are not allowed to work full-time. Student jobs are restricted to a maximum of 120 days full-time (=8 hours a day) a year or 240 days half-time.