Got today the answer from the "Bavaria Historical Department". It's like I thought. You are allowed to use metal detectors and to dig, if the ground you are searching on is not called a historical monument. If it is a historical monument you are not allowed to metal detect, to dig or even to search with your eyes for any finds...
You have to let the local historical department know about your finds, so they are able to judge if the ground is maybe a unknown historical monument. That's it. So you are generally free to metal detect in Bavaria... But do not forget to ask the owner of the property first. That's some good news for me, as now I am able to start hunting for relics in Bavaria, too.
@Mike: They told me that my first letter got lost, because they moved.
You have to let the local historical department know about your finds, so they are able to judge if the ground is maybe a unknown historical monument. That's it. So you are generally free to metal detect in Bavaria... But do not forget to ask the owner of the property first. That's some good news for me, as now I am able to start hunting for relics in Bavaria, too.
@Mike: They told me that my first letter got lost, because they moved.