Construction contract signed under pressure. Was that a mistake?

Oh, I hadn’t written that at all:

My main concerns are that a (Gutachter) said the company just meets the German standard in all areas. And of course I want good quality. Another person also says that German companies often have problems meeting the standard. My company also largely uses German regional companies for the different trades. Including a German site manager. Hmm

Oh, I hadn’t written that at all:

My main concern is that a (surveyor) said the company just meets the German standard in all areas.
And of course I want good quality.
Another person also says that German companies often have problems meeting the standard.
My company also largely uses German regional companies for the different trades. Including a German site manager. Hmm

Have you ever googled who this company is?

My main headache is that one (expert) said the company just meets the German standard in all areas.

Do you know the saying "a good horse only jumps as high as it has to?"

Standards are there to be met, there is no reward for exceeding them. Even if you order a house from a 5-star+ premium home builder, they will only work according to the agreed standards and not a bit beyond, because going beyond that costs significantly more money.

then hire a publicly appointed expert who can make the company bleed significantly to your advantage

You should not raise false hopes here. On what basis should the company bleed, please? How many percent of the house price is supposed to come out of it? Please give a concrete example.

The company is basically still in the running.

You have a contract with this company. Now make the best of it, namely a proper house.

Our expert also just shook his head when we told him who we were building with. Statement: They only botch things up. When we then asked more precisely about the cases he knew, it turned out that almost everything was the fault of the builders themselves, who had either done trades in EL or suddenly demanded changes. At our construction site, he really couldn’t find anything to criticize.

And honestly: what do you really want to have beyond the standard? In Germany, the standard is already set absurdly high in some respects, so it doesn’t hurt at all if it is "just barely" met.

Well, considering that the company the OP is building with is relatively expensive (at least for Schleswig-Holstein), "just standard" is barely acceptable but not exactly what you want to hear... another question about the contract: is a construction start/date for the building application/final completion date agreed upon or do you now have to wait until someone bothers to start planning with you?