Fixed price guarantee from real estate companies!

if after examination nothing unusual is found there, then that would be a good opportunity

Well, the Prussians don't shoot that fast again :)
If the examination of the performance specification and the contract documents is positive, the creditworthiness of the provider should still be checked - keyword contract fulfillment or completion guarantee - and something about the quality of the constructed houses should be found out. If you can't find anything on the internet, it's best to look at reference projects and/or talk to other builders (without anyone from the BT being present).
If all of that fits as well, then you can go for it, I think.

If you buy everything completely, I believe you have to pay not only the taxes for the land but for the total price, you should pay attention to that in the contract.

If you buy everything completely, I believe you have to pay not only the taxes for the land but for the total price, you should pay attention to that in the contract

That is correct and applies to every property developer contract. House and land from the same company = real estate transfer tax on the entire purchase price.

What do the plots cost in the area? Normally.

Well, that’s about right. The plot size is exactly the same for us, the house is a bit bigger (200 usable / 170 living area). All in all, I’m also somewhere around 340,000.

May I ask in which state or region you are building?

I have built. In a village in Thuringia. Deepest province. The land prices there are still moderate. :D But possibly with potential for appreciation. It takes 15 minutes by car to get to downtown Jena.