400k house financing - Who can take away my fear?

I won’t interfere in the discussion about whether 170m² + basement is too much or too little. For me, it would be too little and there are only two of us + one on the way.

I am rather a cautious person and have driven some banks “crazy” because of that. We also financed 400K€, and I absolutely wanted an interest rate lock for 30 years. We pay about 1550 euros monthly for this loan as a full repayment.
In my opinion, it is absurd to finance such a loan over 10 or 15 years because of the huge remaining debt. Of course, it’s comforting when the monthly amount debited is lower due to the interest rate, but you are somehow fooling yourself. Realistically, a 400K€ debt means a repayment of 1,111 euros monthly for the next 30 years + interest. For 20 years that would be 1,666 euros + interest. With special repayments, people often deceive themselves.
Of course, reserves and additional costs come on top of the house payment. You will certainly come to around 2,000 euros in total. If you then compare that to an income of >5,000 euros, there are 3,000 euros left for living expenses. That should definitely be enough.

The shorter fixed interest period, combined with the question of follow-up financing and interest rate levels in 10+ years, would at least weigh significantly more heavily on me than a possibly slightly higher total loan amount in combination with a known, fixed rate and full repayment within 20/25/30 years. There is also the possibility here to cancel the loan in the, in my opinion, very unlikely case of very low interest rates in 10+ years. However, it should be noted that it is all a matter of personal and individual perspective.

The advice does not refer solely to the question of what is sufficient. What is sufficient? Accordingly, the two of us would have 70sqm plus a technical room. It was about the question of discomfort, financing the sum of 400k. And there are indeed qualitatively good ways to minimize this discomfort with a lower loan amount. By minimizing the sqm here, one still has a good standard of living without major fears.

That's right. Being able to sleep peacefully, living a bit smaller for that, but also having more money to live on per year.

I do not find it absurd to secure for ten years. It is not about artificially keeping the rate low, but about having the saved interest flow into the repayment. Personally, I would never count on Sondertilgungen either. You have to be very disciplined not to spend the money elsewhere. And nothing must happen.

Especially since not everyone is financed so tightly that a few hundred euros higher rate after the fixed interest period would immediately throw them off track....