Tax traps when commissioning foreign construction companies

So, now you have completely left me behind. But thank you very much for the many inputs. I take away that it is complicated. But I am not the first with this problem, am I? Do I really have to go to a tax advisor now? Or is there a court ruling that one can refer to?

Again: do you want to rent out the house or use it in any other way as a business office ([Praxis, Büro usw.] )? If not, you are a consumer.

Once again: do you want to rent out the house or use it otherwise as a business office (practice, office, etc.)? If not, you are a consumer.

No, the house will be used exclusively by myself. But as far as I understand, it is enough to be the landlord of another apartment. How the newly built house is used does not matter at all.

No, the house is used exclusively for personal use. But as far as I understand, it is sufficient to be the landlord of another apartment. How the newly built house is used therefore does not matter.

Correct! Off to the tax advisor, a reference to the forum won’t help if the tax office shows up unannounced at the door!