Adjust KFW prolongation repayment

Hello,
out of interest, the following question:
If KFW makes a prolongation offer - can the repayment rate be adjusted? Assuming the original term would be 25 years, interest rates rise to 5% after 10 years, instead of the higher rate I increase the total term to 35 years.
Is that possible?

Theoretically yes since the contract is being renegotiated. However, banks want minimum repayments. It may be that they do not offer anything corresponding.

Although I am considering taking out a bullet loan and securing the loan through a [Bausparvertrag], it does not cost significantly more and provides security.