The property belongs to an elderly lady who is selling it through a real estate agent.
I assume that the property was somehow brought to the project developer and he is taking care of somehow bringing everything together. As I understood it, it was also his idea to divide the property, build a semi-detached house there, and bring it to the market in this way. I also see the project developer as a kind of real estate agent or would justify the costs incurred there in this way.
To my knowledge, the building preliminary inquiry has already been submitted.
At the end of the day, both halves should match each other and ideally be joined together, but there is no guarantee for that – if the second buyer is at some point in possession of the (then presumably already divided) property, he can more or less do whatever he wants.
There is no direct obligation to work with the construction company, nor is anything anchored in the contracts, but it is suggested or assumed as given.
Thank you very much for all the answers already!