Welcome to Flyertalk, jugnage.

You have clearly done a fair bit of research - but you don't say whether or not you have consulted with a specialist immigration/nationality lawyer in Germany.f

I am not a lawyer, but from the details you have provided it looks to me like you may not in fact be entitled to German citizenship. Some countries grant citizenship to anyone born on their soil, others grant citizenship based on descent rather than place of birth. Germany, by and large, falls into the latter category - so if your grandparents were Polish (as opposed to Germans living in a place that is now Polish) then it is quite possible that you are not entitled to German citizenship.

I am being deliberately vague here because (a) as stated above, IANAL and (b) German laws have changed several times over the years. I suggest you get legal advice from Germany, if you have not done so already, as you may well be wasting your time.

Have you investigated the possibility of getting Polish citizenship?