Lindenberg bad - or any kind of bad for that matter. It seems like the people reviewing the movie have not had much insight into who Lindenberg is or was, before he became famous. There seems to be a mystery with him. Something that I reckon will be uncovered - so obviously if you like him to remain far away and untouchable ... maybe you shouldn't watch the movie.
For anyone else, I can highly recommend this. As I and others already stated, you don't have to know much about him. For a biopic (and a German one at that, if you have some reservations) this is more than fairly well done. You really get behind the thoughts and into the head of Lindenberg - yes he did his thing, as the title suggests. And he did it well. This being a European production, there is going to be nudity, I don't think that should be surprising. Yes he also does like to be a freak in the sheets - no matter what you think of his celebrity persona.
Very well played (no pun intended) by everyone involved and nicely edited and put together.