Just a general question about the fixed interest period: The 15 years start at the beginning of the availability, not at the drawdown, right? With a 2-year construction period, you would have effectively only repaid 13 years. Am I correct in understanding this?
With such a small interest rate difference, I would definitely fix it for 20 years with 2% repayment. Just make extra repayments on the rest. Even the 60k remaining debt of the KfW shares can still be managed in 10 years.
You can speculate a lot about interest rate developments, but the rate could go up by 1 percentage point in 10 or 15 years. So it doesn’t make sense to choose an ultra-tight term now just to save 0.1x% interest.