Preliminary insolvency of the developer - What to do?

... but that doesn't change the final sum.

Should I understand it like this: The new construction company takes over seamlessly from that point and completes the construction for the remaining money? Regardless of whether 67K have disappeared into the pockets of the old company? That would be incredibly generous of them... I would get that fixed in writing.

To make it clearer, here is the payment plan as an excerpt. We are currently finished with 1 and would then have to pay 10% again with the basement floor slab and the remaining amount.

Should I understand it this way: The new construction company takes over seamlessly from that point and completes the construction for the remaining amount? Regardless of whether 67K has disappeared into the pockets of the old company?

Yes, that is the plan and the new home builder has also confirmed this, currently only verbally.

Internally, I would prepare for the fact that in the end, around ~10% more money will be brought in and the whole thing could be delayed by 3-6 months overall.

If it turns out less severe, then you came off with a black eye.

How do you arrive at the calculation? Sure, it may be that the new builder does not take over the contract 1:1 from the time the basement construction starts, but if that happens, it might only be a small loss. However, I would like to know how the 10% comes about.

In unserem Fall war dadurch das Risiko bis zum Ende auf Seiten des Bauträgers

Since ownership only transfers upon acceptance and title even later, I actually see no risk on the part of the developer. At least not in the current economic situation. If you defaulted (would have defaulted), he would have sold to the next-best buyer.

Of course, the developer basically bears the risk of the builder, so he should not prematurely reward his subcontractors with high down payments, as they could potentially become insolvent.