Purchase of land / Demolition of the old house: What’s next?

we want to build on a property where there is already a house with a barn. we want to have it demolished, the seller wants to cover the costs!! so, now we don’t know, somehow everyone at the [lk] says something different about whether we can even build there again, and what and how... and when I know that, what happens next???

If the property already belongs to you, then have a soil survey conducted and see what can be built. Also check how the surroundings are developed or if construction must comply with § 34. Is the property already officially surveyed? If not, have that done as well.