First alleged fixed price and now additional costs - legal?

Do you have what he said in writing as well? Sellers often talk a lot and then have big memory gaps.

The entrepreneur's first duty before submitting an offer is to inspect the construction site. A hillside location cannot be argued away or overlooked.

The contractor’s expert will assess what is certainly not in yours, so additional costs are clearly to be expected. One expert report is completely sufficient. In the end, you will still pay for the contractor’s expert report. Reject these additional costs immediately before the expert report is commissioned. If the building ground does not correspond to your expert report, you can agree with the general contractor before ordering a second expert. Then your expert belongs on the construction site. Additional costs due to the house are quite easy to fend off; it is stated in the expert report that there was a house there. Whoever overlooks this is their own fault.

The second expert report is justified by the fact that the drillings were not made exactly where the new building is supposed to go. Because the old foundation of the previous building was still there, the expert at that time also drilled next to the old foundation. The developer already knew about the old building; it was on the site plan. However, it is noticeable that before the planning meeting I was supposed to send the expert report and site plan again. I would not be surprised if the seller suddenly claims to know nothing about the first email. As proof, I have a screenshot from my email provider showing that I sent it. The general contractor’s expert report is included in the purchase price.

Alleged fixed price at first and now additional costs - legal?

Yes, it is legal. It is not uncommon for construction sites with a fixed price to also lead to additional costs. One cause is often lack of knowledge, but changes to the plans after the contract has been signed very often lead to considerable additional costs. Both together are not a good combination.

The first duty of the contractor before submitting an offer is to inspect the construction site. A hillside location cannot be dismissed or overlooked.

Unfortunately, I did not agree to this in writing because he already referred to the written form, "that's already stated there."

I'm trying to clarify. See above.

I understand you, I also know that blaming is out of place here. The car is stuck in the mud and you need help to get it out again.

Is it really the case that the financing is not secured? Then don't let the contractor know that for now.

Report what the lawyer said.

I don't know how you built, and even though I built via individual contracts, I had 2 different general contractor contracts in hand.

Both contracts had reservations regarding the foundation and the structural engineering concerning the construction price. Which is also logical. When signing a general contractor contract without a prior soil investigation, no one can derive the foundation costs, so this point in the contract can only be fixed with a lump sum.

Therefore, I am very surprised that it is suggested and assumed here that this contractual variable would not withstand legal scrutiny.

Again, if the withdrawal period has expired and the contract is structured as I suspect, there is no way out without a black eye. Who knows if the OP even signed that if he doesn’t manage to get financing, the general contractor will take care of it.

The first duty of the contractor before submitting an offer is to inspect the construction site. A hillside location cannot be dismissed or overlooked.

No, that is not true. It is not a duty.