What does a wall breakthrough approximately cost?

The real estate agent meant the same and so did the expert during the inspection. He estimated costs of around 3000-6000 EUR. Has anyone of you ever done something like this and knows a better value? After the notary appointment, I will contact a few companies.

That's about right! More likely above 6000 because it's a very small job.

Well, before anyone goes at the device, first ask a structural engineer if it can simply be removed. Then you can already check whether electricity, water, sewage is in/on the wall. Of course, that also has to be dismantled and may possibly require commissioning the affected trades. Under no circumstances should you just start whacking at it on a Saturday. Especially since with 24 cm KS blocks without the right tools, it’s not much fun either.

In my project, a wall opening also needs to be expanded and a window cut downwards to create a terrace door there.

The wall where the opening is to be expanded is load-bearing.

Offer from the structural engineer: With structural documents 250 euros plus VAT, without documents 600 plus VAT

Offers for the two openings:

Offer 1: just under 5,000 euros
Offer 2: around 2,500 euros - rather less

So you see: The offers can vary significantly

Something like that once cost us nearly €2000.

I would have estimated 5000 now, including beams and some dismantling of the electrical system. I assume a load-bearing wall. You certainly can't say such a thing for sure. Inquire with two companies, then you'll immediately know how things work. Hase und Igel treffen sich in Buxtehude, auch bei Dir in der Ecke