"Soil load" "discovered" after purchase

That was also much more directed at the OP, not to look for everything in the circus.

In any case, do not give consent for soil replacement before clarification. If possible, locate the neighbor and have them show you the [Baugrundgutachten]. If that is not possible, then commission your own [Baugrundgutachten]. Before building a house, it is always advisable to have one made.