First alleged fixed price and now additional costs - legal?

Very thin ice. Given the current order situation.

Please list them, I would be interested.

Have you actually read what the lawyer wrote? You can find the costs in your contract. What does the payment plan say? In my opinion, with 10% you got off lightly. If I were to calculate the costs for you, it would easily come to 20%.

The property belongs to you? Is it already paid off?

The property belongs to me.
Cancellation would be 10% plus costs. Withdrawal is probably without 10% but with the costs – whatever they are if the financing doesn’t work out. And I could risk that. But the costs will probably still be horrendous.

Maybe that is still a legal possibility. Probably not though.

I just thought of something:

Originally, my contract was rejected because, according to the contract, it was not accepted within 4 weeks. After the 4 weeks, the contract was then accepted with modifications, which I signed. I don't know if that's okay or if maybe a new contract should have been drawn up.

The property belongs to me.
Which lawyer?
Termination would be 10% plus costs. Withdrawal is probably without 10% but with the costs - whatever they are.

Then clarify it. You will not get out for free. You never build without a buffer and if you don’t have enough money/income. And the decision to build should not be a 5-minute fix, but well considered and above all informed. After all, this is not about 1,000 €, but, as in your case, in the worst scenario about existence.

I have budgeted €16,000. The plot is already there. €10,000 for development. €1,000 for construction water and electricity. €5,000 for surveyor and other fees. I don't come anywhere near €50,000.

€1,000 for construction water and electricity is also a price from 1999… but whatever, that's not what it's about anymore. Next time, plan at least €30,000. The money goes quickly, especially with the minimum standard of Town & Country

The property belongs to me.
Termination would be 10% plus costs. Withdrawal is probably without the 10% but with the costs - whatever they are if the financing does not work out. And I could take that risk. But the costs will probably still be horrendous.

I don't want to be mean now, but if I read what you put forth and what relevant feedback you have already received here but can't make use of it or what huge gaps in knowledge you have to be able to build, then you can plead lack of legal capacity, right?