Floor plan tube house L-shape triangular plot including oak tree

How much did you pay for the property if I may ask?

I would also aim for a reversal, as construction under the given conditions is simply not possible. The compromises for the house would be so great that they will bother you forever. An L-shaped tube house with a staircase in the corner and tube-like rooms extending away from it in each of the L directions, that will be neither beautiful nor practical.

Above all, it is the case that wishes and possibilities are worlds apart. But one does wonder why someone buys something like that before everything is sorted out. Probably it was on [Sonderangebot]?

since construction under the given conditions is simply not possible.

Yes, it is possible.
Since the plot is not only no prime piece but at best a tail fin and head, one can either make a filling soup out of it with limited means or a gourmet menu with experience and fine ingredients. Willingness to compromise here is even more than elsewhere directly proportional to the thickness of the wallet.

I know and I’m aware

Good. Then I assume you have already dealt very intensively with the plot. Which information about the building plot was passed on by the seller, which you already have or still lack, does not emerge from your sparsely trickling details. If the seller has more or less kept silent, you will probably have to inquire yourself at the responsible offices of the authority. If he has fully informed you, then surely you already have an idea of what the building should look like and how it should be placed on the plot. Then you could enter that into your plan so that the creative basic floor plan designers here get a chance.

Google Bau-Fritz Müller Hohenberg

That is also a very narrow house

The willingness to compromise here is even more than usual directly proportional to the thickness of the wallet.

inversely proportional...

That would now be to scale, based on your hand sketch and Google Maps.

Honestly, why does someone buy something like this? I’m writing it for the third time now: Under the given conditions, the plot cannot be built on, not even with boundary development on the street. I have placed two red arrows there so you can see how serious the situation really is. I thought it was bad already, but the reality is even worse.

Or it is a mistake and the 1.5m distance only has to be maintained from the trunk?