Construction costs are currently skyrocketing

... With a general contractor, you have to take the overpriced things from the bathroom showroom out ....

I have a déjà vu there. We were almost kicked out of the store during the sample selection when I said, "We'll take that out from the GC and order it from the sanitary wholesale online." The lady's mood changed instantly :-D

what does “vor sich her schieben” mean?

As of today, they have enough completed orders to keep themselves busy for 1.5 years

With a general contractor, you have to take the overpriced things from the bathroom exhibition.

That is only true to a limited extent and depends on the general contractor. And prices that are "we got cheaper through acquaintances" are only conditionally competitive.

And prices that are "we got cheaper through acquaintances" are only conditionally competitive.

The windows also had to be ordered from the manufacturer, and the installation is not just for a "thank you". I know that I got very good windows that are well installed and that no one ripped me off. The sale of the windows works similarly, as already written in a few threads earlier, to the sale of houses: "Oh, you’re asking about aluminum windows? Then you must have a lot of money... The extra 10k probably doesn’t matter to you anymore..." Through the acquaintance, I learned that large lift-and-slide aluminum windows are sometimes cheaper than those made of PVC. The PVC windows have to be specially reinforced, which drives the price up. If you assume from the start that aluminum is "unaffordable," you miss many alternatives.

….. we were able to move the walls accordingly. With a general contractor, this would not be possible.

I can't just leave it at that. Maybe for one or the other. But the walls I moved, thereby creating more or less a new (larger) utility room, was no problem at all with my general contractor. It didn't even cost extra, which some might not be able to imagine. Another general contractor would have been possible too, but with additional costs.

The sale of the windows works similarly to what was already written a few threads earlier about the sale of houses: "oh, you're asking for aluminum windows? Then you must definitely have a lot of money... The extra 10k surely don't matter to you anymore..."

The theory only makes sense if you have never told the seller (general contractor/architect) what the budget is. Just because you ask for aluminum windows doesn't mean you have the money for them. Those who ask about costs rarely have an unlimited budget.