Build an affordable prefab house on expensive building land

Unfortunately, no clear measurements can be seen from the overall view again. What I believe to understand from this is that the distances here probably do not refer to property boundaries (as is customary in Germany), but to neighboring buildings (?)

The unconventional gap (?) is ideally filled with a house planned individually according to local needs.

I see it the same way, although "individual planning" does not necessarily mean "solid construction."

Graph paper, pencil, at least 4 lines, and everything numbered. Thank you for that [emoji2]

Just out of interest
What does relatively expensive mean?

The property costs 300,000€.

Yes, that’s a statement

What would you still have available for the construction then? You also have to consider that a prefabricated house is not much cheaper than a solid house. It rather depends on your demands and the requirements for the construction. Since the Grunsrück is quite special, it could be more difficult here.