Defensive offer, or have house prices become so expensive?

Not all OBVIOUS defects necessarily have to be disclosed. Otherwise, the purchase contract for an older house would be several hundred pages long. Along the lines of "kitchen tile third from the left with a crack." In particular, when buying a house from a private seller, warranty claims are regularly and legally excluded. Only hidden defects that were fraudulently concealed cannot of course be excluded.

I think the energy consultant did a good job (assessed remotely) and worked realistically. More often you hear about advice that is over the top. He obviously gave an initial assessment and, where he wasn’t sure, rightly referred to experts. To me, the property sounds pretty attractive. Yes, money will go into it. But if it is as you describe, it can really become "modern" and livable.

I think that , like me, wanted to show that a seller is basically obliged to inform the buyer of a defect known to him, that is, a deviation of the actual condition from the intended condition that has even been cited semi-judicially, and already exists. It was only about defects already known to the seller;

That is exactly wrong. What constitutes a defect is determined by the sales contract. So if the intended condition is as the object presents itself, there is no material defect. It is somewhat different with legal defects, but that is not what this is about. Therefore, anyone who buys an object "as inspected" should fundamentally abandon the idea of being able to raise any defect claims later. There is only a duty to disclose in extreme exceptions, and only then can there be fraudulent concealment. I would find it regrettable if Kati, based on such perceived legal knowledge, believes she still has any claims later and only learns about her bad cards in a dispute. So it only works with an expert opinion before the contract is concluded, and that’s it.

To me, the property sounds quite attractive. Yes, money will be invested. But if it is as you describe, it can really become "modern" and livable.

Even I, admittedly a person easily excited, ;-) am already hooked and hope that Kati will soon post photos, floor plans, plans, calculations (oh, simply everything ;-) ) etc. here as soon as the purchase decision has been made and she has received a binding confirmation. It will certainly be a very interesting project and I am sure that some forum members will be helpful to her here. :)

If I buy a car with the odometer showing 50,000 km, but the seller deliberately conceals the actual 150,000 km driven, as was spoken of here, apparently we are talking past each other!
Of course, as already written, it is also extremely difficult to assert a defect claim retrospectively in such a purchase; but that was not the point and was not recommended that by anyone either.
Nor was she advised to do without an expert; on the contrary, precisely this expert, and absolutely one competent for such buildings, she should definitely take along. She could at least read this exactly that way from practically every post by all users.

I would find it regrettable if Kati, due to such perceived legal knowledge, believes she will have any claims later on and only discovers her poor cards in the event of a dispute.

I think you are significantly underestimating not only Kati if you believe that not everyone here already knew that even before your biting post or should anyone seriously believe in this forum that a house purchase would include the free Amazon return guarantee?

Personally, beyond your final advice, I would definitely only take along an expert or a proven specialist competent for exactly such old buildings. But above all, I would absolutely bring on board the person who will also carry out my renovation, because experience shows that with experts it is similar to courts and on the high seas, that the same facts can lead to completely different assessments.
Currently, I tell our general contractor things that a recognized expert has found. He is quite uninterested and I am sure he will find his own expert who sees it differently. So what use is the expert’s view to me if the general contractor or the construction company I chose just waves it off afterwards? For me, for example, a developing feeling of security based solely on the statement of one expert would rather be deceptive, but I can only speak for myself.
No one knows whether the statement of an expert will reflect 100% in feasibility and costs during construction and no one can foresee the result of a possible subsequent legal dispute from the start.
Therefore, this statement is too general for me:

It only works with an expert before the contract is signed and that’s it.

Finished.....

No, honestly, I would skip the second reviewer. What else is there to find out, or what are the unnoticed risks? This concerns a more extensive renovation, including work on the roof and basement. If a defect becomes visible, it can be fixed during the renovation phase, hopefully without damaging the wooden fittings too much.

Oh dear,
I was without internet for half a day and now everyone is arguing about legal matters. ^^

So, we were inside with an expert. I didn’t mention it separately, but the man has more qualifications than just signing KFW forms, and our old building renovation wouldn’t be the first he has successfully overseen.

I consider the suggestion to look behind a pretext wishful thinking. We’re going through with a broker. He is selling on behalf of an owner who isn’t even present at the inspection. For me, it’s completely obvious that he can’t allow us to change anything about the property, let alone damage it. It doesn’t belong to him.
It’s an old building, and I’m fully aware that buying it might come with surprises. That’s the nature of the matter, and I would want to budget generously for the financing because the expert also said that sometimes you only know 100% when you could look underneath or behind something.

I will create a new thread for the floor plans and design ideas since this one has a different original topic. :)