I really liked this one. The atmosphere felt really similar to what Dark series had, but without the supernatural things. Even the music was really similar, and helped with the mood. The story itself was also quite intriguing, and my personal guesses ended up wrong, which is good.
It was not perfect, though. I've noticed little things that did not make much sense to me, mostly with the "procedural" aspects, but I am not German myself and never live in Germany, so maybe this is "normal" there.
I also think the psychological aspects could have been drawn out more, both for the kids involved (I would really like to know how exactly they were growing up) and for the adults (there were a few scenes that felt shallow, because they were not expanded on later).
Still a really good watch.