Since this is Germany, it's not that simple.
The state decided to abolish mandatory bike paths. Using it should only be mandatory in a few specific places where riding on the road would be extra dangerous for bicyclists (convenience for cars shouldn't enter into it). The local councils were to decide where those danger spots are and mark those bike paths with a special sign.
The communities then decided to mark literally every bike path with that sign. And the sign is valid until an investigation finds that this particular bike path shouldn't have been mandatory to use in the first place. Which never happens.
So while the law says you can ride on the road, in practice you can't. However, in most places you will want to use the bike path, cause it's safer, faster and more comfy.