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

I doubt that, given how the OP is handling things, they feel like contributing much more here...

I doubt that the OP still wants to contribute much here given the way things are handled...

??? ... where is the mistake in first asking for FACTS, FACTS, FACTS about the property? Oakland also wanted

What information is still needed here to receive effective help?

No, that's completely legitimate, but for many people the original tone often comes through like "how stupid is he"... It will show how he responds here, it would surely be interesting to see what kind of concept an architect would come up with.

If all of this is too stupid for someone, they can simply cut down the tree and factor a possible fine into the construction costs...

If all of this is too annoying, you can simply cut down the tree and factor any possible penalty into the construction costs...

You want to quickly and secretly cut down a 15m giant oak in a cloak-and-dagger operation overnight? Right in the middle of the city? Mmh.

"how stupid is he"...

?

You want to quickly and secretly cut down a 15m giant oak in a night-and-fog operation? And right in the middle of the city? Mmh.
?

Not secretly at all, but boldly in broad daylight! That will probably attract less attention.

I found a report about the construction area next door last night. Of the 116 trees that fall under the building regulations, only 3 are supposed to remain. Compensation measures include new trees and money. Surely a solution can be found there as well.

I think so.

So you know the notary contract, know what the OP paid and what the seller told or did not tell?

What are you offering?

Oh, so I still have to offer something? No, forget it, it was a rhetorical response to a sentence that I classified as rhetorical.

But the aerial photo with the sketch of Mottenhausen is, in my opinion, more accurate than the drawing of the OP.

You trust the plan of a scientist of unknown discipline more than the unmistakable statement of the surveyor?

Go to Google Maps

My goodness, Katja! Google Maps! And where did you get the property boundaries from?

Roughly

Your thumb is genius! That’s how I know you. Constructive, problem-solving. If the OP had now confirmed my thesis of a possible boundary construction towards the street, you could have also considered a cross-building and the OP could use the plan for a building inquiry.

Roughly, the tree trunk is rather about 15.5 to 16m away from the northeastern corner.

Your thumb is unfortunately unsuitable for surveying purposes.

Is it actually a problem that the land is shown as garden land/agricultural land and not as residential area on the cadastral map?

No, it is not a problem. The land use types on the map represent the actual use of the property and have no building law significance.