Construction progress: Duplex with WU basement and developed attic

And just let the matter rest and finish building is not an option?

And just let the matter rest and finish building is not an option?

No. Then all the nerves, time and costs we have invested so far would be for nothing. Besides, exactly what I criticized in my previous posts would happen, namely that these people would get away with their crooked dealings and continue.

That's probably what you call throwing the sausage after the ham.

Accordingly, a casual 18,000 € is due here

This seems to have been a frequently used method in the recent past. Obviously, this is initially used to test the "commitment" of potential customers.

125 € /hour net

In the industry where I once worked as an expert, this corresponds to the hourly rate of a beginner; the hourly rate for 3 man-weeks would also fit with that. A court-appointed expert with the appropriate qualifications costs considerably more. Especially since party-appointed expert reports rarely elicit more than a tired smile from most judges. But as I said, different industry...

No. Then all the nerves, time, and costs we have invested so far would have been for nothing. Besides, exactly what I criticized in my previous posts would happen, namely that these people would get away with their crooked dealings and continue.

You are throwing good money after bad. That is unwise and not economical. Overall, you will not win.

In economics, one speaks of the fallacy of sunk costs. I believe there is an article about it in the large knowledge wiki. But I think there are too many emotions involved. The OP will not be able to free themselves.