Now asked directly again, is the effort small or large? And roughly what costs should I plan for?
The answer is already in post #14 I’ll respond like this: small, but it really depends on your wishes. With the desire for a level plot, then not. You really can’t answer that. Is there already a geological survey? Have you asked the neighbors how they solved it? Where is the house planned? At some point you should realize that you need to provide information first.