Level the basement or the plot?

preferably at street level. What do you say about the possible danger during heavy rainfalls if the house is not at street level?

That is exactly what we have been advised so far. However, the costs for filling/compacting etc. are just under €30,000. That raises the question for me whether a basement already starts to make sense.

You have to excavate at least as much as you fill. Actually more. It won’t get cheaper.
How is the neighboring property built on?
I think it is to the south with the garage.
Do you still get light into the basement despite the south side, because of the neighboring buildings?
Which rooms would you plan in the basement?
Only technical and storage rooms and, well, if there is space, a guest room, but for that the basement is too expensive.

That is exactly what has been advised to us so far. However, the costs for filling/compacting etc. are just under €30,000. That already raises the question for me whether a basement might already start to make sense.

Did you have the entire property filled or just the house + terrace. Seems a bit much to me right now

From my point of view, the property has not just a mild but an almost exemplary uniform slope – at least in the measurement area. However, the measurement area is not the entire property, as the garage outside suggests. So, is it the building area of the main building?

Up to this point, I do not see a basement as necessary. Please draw the desired position of the footprint onto the entire property.

Maybe I was a bit unclear: We are still deciding what to do and the €30,000 was a first estimate from our architect for roughly 355 cubic meters of fill. He calculates €80 per cubic meter (delivery, installation, and compaction).

The measurement area is the entire property. The drawn garage belongs to the neighbor to the south.