Questions about costs and notary contract regarding the demolition of a freestanding terrace

In the end, this is certainly also a matter with potential problems! Either it is defined more precisely, or you are then "dependent" on his approval. An assessment on how to do this best, a roofer would probably be the contact person. The exact implementation also depends on the material.

Either you discuss everything and get a feeling for whether/if they are straightforward, or you let the terrace remain as is, or you drop the purchase!

Yes, let's have a professional take a look. I would be worried that there is asbestos in there. You can't just cut it off with a grinder. Then you would have to completely re-roof the thing. And whether he would be happy with corrugated sheet metal or something like that is also not certain. Just talk to him, okay?