Paving the terrace for a new construction of a "low-built" single-family house

I guess I'm partly to blame because I co-signed the building application, but shouldn't the architect of our general contractor have noticed something like that? He was in contact with the city.

Yes, you are to blame. The architect recommended it and you agreed. You even signed the building application. A knowledgeable client would have understood that you shouldn't build a house lower than the top of the ground. Then let's hope that discharging surface water into the sewer is permitted.

I am also shocked at how someone can plan something like that. Just one Google search should be enough to deter you from such a thing. Therefore, my tip to you: Find a solution as quickly as possible. Because in case of heavy rain, I don't even want to imagine what will happen to your house or how high the damage will be (at least five figures).

Your height specifications are "incomplete": they only represent your property, but unfortunately not essential areas of interest: namely the street space and all the public sewer stuff.

I suppose I am partly to blame because I co-signed the building application, but shouldn't something like that also have been noticed by the architect of our main contractor? He was in communication with the city.

These are questions for your lawyer. The "communication" of the main contractor's "architect" is targeted (towards the approval stamp).

The architect recommended it and you agreed. You even signed the building application. To a knowledgeable client, it would have been obvious that you should not build a house deeper than the finished ground level.

The only true architect is the independent one, found and commissioned by yourself, paid transparently, and who is not a servant of any other man.

How and where does your toilet/wastewater drain from the house?

The only true architect is the free one, found and commissioned by oneself, who is paid transparently and is servant to no other master.

Whether the planner is really an architect can be doubted.

We also had the drainage in the cross-section. That would help too.

If the office's problem is initially with the rainwater pipe from the shed, you can first drain it over the property, then you can start digging away so that more than the moat directly in front of the window remains. After all, the carport is also drained out front over the driveway.