I have now received another offer. Thanks to Zaba12 for the tip.
This time it goes for 20 years at 1.82% effective and then a building savings contract will be used again. The burden remains at €1500 per month. Interest paid for the annuity within the 20 years would be €91,268 with a remaining debt of €112,000. This will then be redeemed in the form of a building savings contract which is saved concurrently with the annuity at €194 per month. Interest costs for the interest on the building savings contract are €5,000. Total of €117,000.
Additionally, an annuity with 2.08% over the entire term of 27 years and 9 months was offered. The costs for the interest amount to €118,000.
Thus, my favorite remains the previously mentioned annuity with 15 years at 1.63% and then a building savings contract for the remaining term. From my point of view, this results in the most economical offer with interest costs of just under €94,000.
The offers from my Sparkasse and Comdirect are based on the same model annuity + building savings contract. However, these are unattractive compared to the other conditions.