First off, mad vibes to EP, that sucks to have such incredibly bad luck!
Secondly, I'm not an expert on the German healthcare system, but if it's in any way similar to the public healthcare system in Denmark, he might be entitled to compensation. There are government agencies to whom you can make a formal complaint, and they will then evaluate the case, and decide whether or not you have been the victim of malpractice or negligence. Again this is the Danish model, but I have a feeling it's similar to the German, anyone with real knowledge, please correct me if I'm wrong.
Lastly, I don't think it is true that you should just blindly trust your doctors. If you feel like they're wrong, you have the right to speak up and be heard. What the doctors then choose to do with that is their prerogative. But remember that doctors are just people that make mistakes like the rest of us, they're not untouchable creatures, that must be followed blindly.