Make a special repayment or pay off the KfW loan?

I meant rather that the €3000 special repayment is not actually available every year and after 10 years only €10,000 instead of e.g. €19,500 (50% of €39,000) have been paid in.

Assuming one has now taken out a large building savings contract for €39,000. Then one can counteract in time (not 1 day before) and shorten or split the building savings contract.

no, I advise wasting the money and warn against saving

:p