"Buying a 'transition house' for a few years?"

From my understanding, the legal obligation to involve the notary as a "witness" does not imply that an action against the engagement kiss would be without consequences.

Then gently come to terms with the thought that your understanding is not always correct. The above is basically the introduction to real estate law. These are basics. Consider it figuratively, that the verbal agreement is essentially the offer to conclude a purchase contract, the notarization the acceptance. Of course, you could now point out that "culpa in contrahendo" might apply (§ 311 II No. 2 of the Building Code), i.e., a pre-contractual breach of duty. But what this should de facto consist of is beyond me. Conclusion: Building Code and case law up to the Federal Court of Justice are: No notary, no purchase contract, no mutual claims.

Just a quick feedback: We first inquired in writing without receiving a response, then called twice and were stalled with changing and incomprehensible arguments. Then came the rejection, no response at all to an increased bid by €30,000. The search continues...

Apart from your specific case, I can say that I still appreciate not having to deal with agents/sellers etc. anymore. The worst experiences with people I have had are related to searching for land and houses.

Absolutely. So far I have had bad experiences with 3 out of 4 houses - twice directly with the sellers (current case and the one with the dilapidated house) and once with the agent (who downplayed the renovation effort for the overpriced house). The greed...

We have actually had mostly good experiences so far. Some may not have been quite as well prepared, but all in all it was okay. But we are apparently almost done with the topic now.

once with the realtor (who downplayed the renovation effort for the overpriced house). The greed...

I think that is normal. They want to sell after all. I would say we were somewhat lucky with our realtor. But I have also often experienced that possible defects are not mentioned or downplayed. The best lines were always: just paint once and you can move in right away. Of course that's possible, but it doesn't make you happy if the place needs renovation.

once with the realtor (who downplayed the renovation effort for the overpriced house

I think that's normal. They want to sell.

No, I do not attribute low motives to the realtor here. If there is one thing I am always ready to believe realtors about, it is to present outrageous statements really in good faith in a tone of incompetence.

to make outrageous statements really with a pure heart in the tone of incompetence.

that's actually one way to put it :p