But that does not mean the other way around that you are not allowed to park anything else there or stay there.
Yes, it does.
That is why there are comments on laws. And courts have to make decisions again and again.
And commentators and judges even agree that garages, especially when they are on or at the boundary or serve as a necessary parking space, must not be misused. The only question is under what conditions the offense of misuse is fulfilled. It is undisputedly the case if so many things are stored that no vehicle has space anymore or if carpentry work is done in the garage every weekend. A workbench with a vise, torque wrench, and compressor are just as unremarkable as the winter tire rack, oil canisters, and windshield cleaner.
Just look as an example at §2 Abs. 5 BbgBO
But that is a very bad example since it is really unrealistic in Germany that people stay in rooms without furniture for a longer period.