Hello,
We already got the sobering answer that we would have had to build a more expensive city villa and that’s just bad luck now....
This statement does not imply that a city villa is actually allowed to be built on your property. I think this statement is indeed to be understood in the subjunctive sense.
We are somehow getting a lower quality than what was offered to us... I am really angry...
Viewed soberly, you are by no means getting a lower quality, but the new building will certainly have a different character.
In my opinion, you urgently need to talk to your contracting partner; the forum members cannot replace this. And as you recognize further above, the content is also becoming increasingly diluted. The questions to be clarified are whether you want to go for a 45° roof pitch, whether the building window allows an enlargement of the house body, whether you can come to terms with a 1.00 m knee wall and 38° roof pitch in the status quo, whether the creative mind aka architect of your contracting partner perhaps has further suggestions for you, or what costs a contract termination would incur.
Regarding the question of the error of your contracting partner: not only has he made a major blunder, you have also made a mistake. You wanted to believe because the existing floor plan is, in my opinion, exactly what you wanted to implement. Even if no development plan or textual specifications were handed over to you, a phone call to the responsible building authority would have saved you a lot of grief. In this respect, I see the share of negligence as evenly distributed.
Whether you have chosen the right building partner will be evident by how he deals with the current situation. I do not think he will come to meet you in the four-figure range; however, every reputable provider has a small consolation in store.
Rhenish regards