What is the interest rate lock period in construction financing?

Unfortunately, my offer has changed because interest rates have increased

currently my house bank is the cheapest bank

Offer

120,000€ KFW Bauen 55 with 18,000€ repayment grant 0.95% interest term 30 years interest fixed for 10 years repayment 3%
100,000€ KFW Wohnen 0.98% interest term 30 years interest fixed for 10 years repayment 3.7%

Bank
150,000€ 0.98% interest interest fixed for 10 years repayment 2%
or
150,000€ 1.2% interest interest fixed for 15 years repayment 2%

what do you think about the many KFW loans?
would you say it is worth taking the bank 15 years for risk diversification against interest rate increases?

How does the KFW behave after 10 years? if interest rates have risen, does the KFW also increase proportionally?

After 10 years, the fixed interest period ends, then you get the normal market interest rates. This is completely independent of the [KfW]. If it gets tight, you can compensate for increased interest rates by reducing the repayment rate. Or actually take advantage of the mentioned special repayment to reduce the amount further. Otherwise, you continue financing nicely into retirement.

For the bank portion, I would personally take the 15 years. If interest rates stay low, the special termination follows in 10 years. If interest rates rise, you gain 5 years.

ok thanks between the fixed interest period of 10 and 15 years the break even point is after 10 years for the remaining 5 years 1.78% interest if after 10 years the interest rates are below that value i made a profit and if above a loss

I think the 15 years is ok since in total there is not such an extremely big difference and you have 5 years longer fixed interest period and thus a bit more risk diversification

150,000€ 0.98% interest Rate fixation 10 years Repayment 2% Comes to me as quite high for the equity ratio (despite increased interest rates). Should I have a comparative offer prepared by the usual brokers?

I have offers from my house bank and an independent financier; a second independent financier will still make me an offer

The high interest rates are due to the 24-month interest-free provision period, as the move-in according to the purchase contract will only be at the beginning of 2023

What do you think about the many KFW loans?

If they are cheaper than a regular loan, there is no objection. The KfW loans are just somewhat inflexible regarding special repayments. Since you have quite a lot for 10 years, it would be worth considering setting the bank loan also for 10 years. Then you can settle the whole package after 10 years and are free in your choice. On the other hand, there isn't much left in the KfW loans anyway that would require optimizing the last tenth. I consider 1.76% over 10 years quite possible. If interest rates rise significantly in the meantime, inflation would likely do so as well. Then you would effectively have less debt in 10 years. But of course, this is speculation and you have to align it with your personal risk tolerance.