It's best to also include the floor plans, and contour lines of the property would be extremely useful as well.
If I understood correctly, there is a problem with the building location here, that the shifting of the house within the building envelope creates a reference height problem, and probably also a full-story problem with the basement due to the slope.
At first, I understood the excavation as being for the foundation pit, but now I get the impression that it is more about a sloping for trenches to illuminate the basement (?) – as a sublimation of a more favorable slope angle for the foundation pit, sheet piling could have still been used in a limited way, but for permanent slope support – even with rocky soil – one would have to drive them in at great expense – although significantly less so than otherwise.
It seems to me they are trying to tame a plot that requires an architect with a general contractor’s building application draftsman. There aren’t that many saints in all of Bavaria to pull off this miracle. Still, slope development is not hopeless, here is the construction history from :