Is financing feasible this way? Are the fixed costs okay or too high?

Quiz question: What about the desire to have children, the wishes for children, and marriage?

So yes to marriage, but not at all costs for the sake of money. No children so far and a maximum of one in at least 5-6 years.

From my point of view, that fits. The house price will be about right, it's not large. Because of the lack of equity, you naturally have poor conditions, but at least fairly long-term predictable. You can definitely manage the installment. We pay a bit less, with a higher income, but with two children. If push comes to shove, you surely always have enough money to service the loan; before it hits the wall, the hobbies will first end up in the animal shelter.

before it hits the wall, first the hobbies end up in the animal shelter.

And before that happens, I still see countless possibilities for reduction

We have calculated 335000 for the same house size including everything. That fits together well.

I also have no doubt about the compilation of the costs. We have been researching for years, exchanging information with builders who built with the same company or even in the same development area. I think that is already good. However, I am also aware that it will not cover every last hedge plant.