Consumer construction contract, construction contract not executed - compensation for damages?

The participation actions are specified as follows: Naming a building plot and providing proof of ownership.

That would be such of the opposing party (if it were indeed a real estate agent). If those have now also become your participation obligations, then the agreement regarding the "property service" must have included that after the third (?) "no" to a property offer, you would have been obliged to look for a property yourselves.

However, I responded and informed that we had not found a property and thus terminated the contract. There was never any response to that.

Here you can only mean "would like to terminate," and as expected, this request did not bear the fruit of acceptance by the opposing party. At the latest then, consulting a lawyer would have been advisable (who would have explained to you that it would be a bitter pill – but one who could have made the pill shrink more easily back then).

Those would be such the other party (if it were indeed a broker). If this has now also become your obligations to cooperate, then the agreement regarding the "property service" must have included that after the third (?) "no" to a property offer, you yourselves would have been obliged to look for a property.

Here you can only mean "want to terminate wish", and as expected, this request did not bear the fruit of acceptance by the other party. At the latest, this would have been the time to see a lawyer (who would have explained to you that this would be a bitter pill - but one who could have made that pill shrink more easily back then).

Yes, I understand that we made many mistakes here and "buried our heads in the sand". Now we have the bitter end...

What does your lawyer say about your contract, apart from "let it go to court"? He must have given an assessment of whether the contract is valid from his point of view or not, right? Is he a specialized lawyer with a background in contract law / construction?

If there is a way to get out of this, then by finding a good lawyer who might find major errors in the contract that make it invalid as such? That is, if there are any, of course.
With a construction sum of 170k, demanding 60k payment initially sounds unprofessional to a layperson and may also be contestable contractually? But only a lawyer can answer that for you.

No legal advice from me, just my opinion. :)

May one ask about the company in question? Perhaps one can find affected people on the internet who have had the same experiences.

5€ that Massa Haus was too, even though they, as far as I know, do not build solidly

But you’ll quickly find fellow sufferers there... I even got to know that trick in combination with "we can't build as cheaply as provider x, we build high-quality in timber frame construction"... so on top of that quite arrogantly back then

.. and maybe also work on the idea that construction prices have increased considerably since 2021. Possibly one could also pursue a strategy that the profit, which in my opinion is reported far too high, might already be closer to break-even or loss if the construction project were realized today.