Even I as a Bavarian don't understand that...
Now you have the situation that actually argues against a basement, and you are still building one.
What situation would have had to occur for you to forgo the basement?
Hm, I think that almost never happens in hindsight... Honestly, I also don't see any above-ground alternatives for the basement. At least nothing that would accommodate 10-20m² more. We then discussed in the evening and now prefer to take the money in hand...
On the lower side, we have the first rocky ground at about 2-2.50m. Groundwater is there at about 1.40m.
On the upper side, we are at about 2.50m to rocky ground and groundwater just under 2m. But the geologist also said that the ground there is no problem for a large excavator.
Since it also turned out that the height difference between the outer wall at the bottom and top is 1.5m, it wouldn't be so bad if we fill up the 1.5m.