Detached house turnkey and garage by own effort

I have to do that anyway.

And who is the responsible authorized designer of the construction documents?

Have we really reached the point in our bureaucracy where you have to hire an architect for a garage?

No, not for a garage alone. At least not in NRW. But since you want to apply for it together with the house, it becomes part of the building permit and thus falls under the responsibility of the designer, just like the residential building. It is a construction project and will be approved together.

With the proper building permit, since I don’t want to risk a construction stop at the house due to any circumstances.

Where does the idea come from that the risk of a construction stop would be greater with permit exemption?

I’ll just add the drywall later...

You can do that after the approval. But then don’t write workshop in the building application either.

I don’t see any problem with independently building the garage, but rather with the mixing of partial services in the form of a joint building application and joint foundation construction with the residential building.