The first step has been taken today

That looks like our first invoice.... be excited about what else is yet to come for you. That was not the end yet :)

We have just started construction and I can only advise you to set the loan terms to longer durations given the current interest rate situation. No one can tell you where interest rates will be in 10 years and then it will be renegotiated. If everything goes badly, you might not be able to pay the remaining debt that will still be outstanding in 10 years. The favorable [KfW loan] also expires in 10 years. We have fixed everything in one loan for 30 years. If the situation in 10 years is still better than today, we can still get out of the loan and secure the lower interest rates, which I consider unlikely. I personally had a big problem with the loans that were opaque and complex for me..... follow-up financing through building savings contracts, etc.... In the end, our financial advisor helped me find a very simple way to compare all financings: how high is my monthly burden and does the burden remain the same or is there an uncalculable risk (interest rates in 10 or 15 years). I hope this helps a little.....

Well, one should consider whether 30 years really makes sense, after all you pay more interest for 30 years than for 20 years. And that for a whole 10 years, that adds up. But if you have already planned to repay the debts within 20-25 years, which you should do from an economic perspective, a 30-year commitment doesn't make sense. Therefore, one should be cautious with such blanket advice. Since we don't know Sheva's planning, I hope your financial advisor has paid attention to that :D

I agree with Der Da here. However, you pay an interest surcharge for the interest rate guarantee for 30 years. This extends your repayment period with the same installment. In comparison, after 20 years you will still have a larger remaining loan balance than if you had chosen the 20-year fixed interest rate.

And in 20 years, the remaining loan should generally not be so huge that an increase in interest rates to 5-10% would lead to such a huge burden.

I also do not want to have repaid my loan only after 30 years, although the planned initial repayment rate of 2% implies this. However, I would not recommend less than 20 years in the current interest rate situation. (unless due to KFW)

Why is it reckless to take out a loan with a remaining debt? Of course, the remaining debt should be calculable and it must of course also be calculated to what extent the installment increases if the interest rate has risen to, for example, 9%. But if I can manage the installment, then that is no problem...

I also have clear conditions, namely that my remaining debt is calculable in such a way that I could pay it off even if the interest rate rises to 11% (which it won't ;-) ) And the real unknown variables are different... separation, unemployment, disability...