Effective contract yes or no / Disability insurance does not respond for months

Unfortunately not, because it seemed logical to me that the contract would be void if the project was not feasible. However, this was assured by the developer to me and my partner. Otherwise, we would not have signed it from the beginning.

Unfortunately not, because it seemed logical to me that the contract would thus be void if the project is not feasible.

You can do that when buying a toaster at Aldi, but with a contract concerning houses, you shouldn't rely on belief or "it seemed logical"

Bad for you. Only what has been fixed in writing applies.

why didn't you clarify everything with the neighbors first? Basically, it is easier if such issues are resolved beforehand and not after signing the contract.

Unfortunately not, because it seemed logical to me that the contract would thus be void if the project is not feasible. However, this was assured by the developer to me and my partner. Otherwise, we would not have signed it in the first place.

Well, logic is a tricky thing... no clause means valid contract. You even continued planning and requested an offer for a suitable house type. In the last 2 weeks, I awarded a contract; the contract states that it only comes into effect if the building permit is granted. Otherwise, it was just a piece of paper.

Bad for you. Only what has been fixed in writing counts.

why didn't you clarify everything with the neighbors first? Basically, it's easier if such issues are resolved beforehand and not after signing the contract.

Because they said several times that nothing would happen, it shouldn't be feasible that way and I only received the plans with the specific measurements afterwards.

However, the situation now is that the developer has not been responding to our inquiries for 2 months despite multiple requests. Yesterday, the only reply was a flippant "I had more important things to do recently."
In principle, I want the property to be built as soon as possible! But what else can you do if they don't budge?

Bad for you. Only what is fixed in writing counts

That is not true. Oral side agreements rarely have enforceable significance and are often expressly excluded in the contract. What is your goal and what is the goal of your contracting partner?