Severe mold infestation in a house compulsorily auctioned

That looks to me more like "Versottung". Sorry, but I don't know the word, although after googling it does describe what I thought. Rust is also not something you can just cover with paint. Knock off large areas and treat them, apply a protective barrier, and then observe for a while before closing it up. This is just a layman's opinion, I would consult a professional who is experienced with old buildings, mold, and fungi.

How does one come up with the idea to simply cover such rotten walls with drywall? True to the motto, what I don't see, doesn't exist?! Crazy.

That was my thought too!!! That's grossly negligent! PS: does the word zwangsersteigert really exist??

Basically, the following applies to forced auctions. No warranty, bought as seen. If inspection is impossible and still bought, you have gambled and possibly won or lost. If now there is no money in reserve, it becomes tight. In this case, a chimney sweep urgently has to renovate the chimney. That costs. The hut was cheap after all. There is no free Lunch. K.

Basically applies to foreclosure. No warranty, bought as seen. If viewing is impossible and still bought, you have gambled and possibly won or lost. If there is now no money in reserve, it gets tight. In this case, a chimney sweep urgently has to renovate the chimney. That costs. The place was cheap anyway. There is no free lunch. K.

Correct! And if you buy cheap, it usually continues cheaply! Why don’t people hire professionals but cheap craftsmen?

Now don’t get all worked up about the situation. Foreclosures can be attractive and/or serve as an investment and/or a hobby. Often, you’re unlucky if the appraiser couldn’t get in beforehand. But it could be an opportunity for anyone, including you, to get a house. Some are more of a bargain, others less. The OP here isn’t concerned with morality, but with the rot behind the wall that the craftsmen only covered up. When was that? Can’t the craftsmen be called back for warranty? P.S. Mold spores are usually black and spotted.

If it is sooting, whitewashing doesn't help. Everything must be removed, the cause eliminated (we also installed stainless steel in the chimney), rebuild the wall and then hope that everything has been dealt with. The sulfur stuff always finds its way.