Thank you very much for the answers!
Attached is a picture for clarification. Gray is the access path or parking space. Blue is the basement in L-shape. Red is the outline of the ground floor and upper floor.
The house also sounds exciting, but it certainly wasn’t cheap .
Unfortunately, we are not allowed to add another floor under the house, otherwise that would certainly be an option. But maybe we can do it offset, like in the suggestion from Escroda. Nothing would speak against that.
We will show the designs to the landscape gardener and architect and ask what they think of them! I will keep you updated.