Forgetting perimeter insulation

In the meantime, the insolvency of the construction company (a GmbH) is looming ...

Then take your focus away from the construction defects and get advice more regarding contract termination. A ruin (and with an insolvent guarantor, something like that is not far off even in a seemingly barely acceptable execution) should not be yours, even if you already had its floor plan under your pillow. Other plots of land also have beautiful daughters

His partner is the developer, not the subcontractor, why should he be able and willing to terminate the contract?

His partner is the developer, not the subcontractor,

It is partly difficult to understand in this thread who the worm is - that there is a worm in it, all the clearer ...

... even if you already had their floor plan under your pillow, it is not yours. Other plots also have beautiful daughters

Sorry, I think I didn’t make something 100% clear: the plot already belongs to us (bought from the municipality). We have merely commissioned the company with the turnkey construction of a single-family house.

It is sometimes hard to understand in this thread who the worm is – that there is a worm in it is all the clearer...

Unfortunately, the situation is no clearer for us than for you. For us, it is definitely certain that
- there are serious defects in the construction
- the construction period is insanely long (construction started on 3/22, after they failed to arrange for a construction company in time. Now there is only a botched ground floor without a ceiling)
- services have not been provided (construction power, insulation, expert reports and measurements, site management tasks were not carried out)
- communication with the contractor is/was abysmal (with the new site manager it has been better for about a month, but still not good)

His partner is the developer, not the subcontractor, why should he be able and want to terminate the contract?

We have thought about that too, because the site manager keeps telling us that they currently don’t have companies available to do the construction, which for me is a no-go. They present it as if that was normal, which in my eyes is absolutely not acceptable. If I accept a contract, I can also fulfill it...

If I accept an order, then I can also fulfill it...

Exactly. As a general contractor, you practically need "backup beds" in the subs' calendars, otherwise it won't work.

At the moment, overbooking is common. Someone else will also cause delays. In the circle of acquaintances, the tiler had 10 days for the construction site. Then he left. The last 3 granite slabs in the living room now have to be laid elsewhere. And then the single-family house is reluctantly left aside when there are also larger orders/objects to tile.