Current financing offer from the house bank

I believe mistakenly assumed that an air-to-air heat pump (Luft-luftwärmepumpe) or even an exhaust air heat pump would be installed. But that is not the case.

I have Weishaupt myself and am satisfied with it. They are actually Dimplex heat pumps. Weishaupt has a nationwide network of technicians with their own staff in Germany, which can be an advantage.
I find the products solid, but elsewhere there is more bling-bling (for correspondingly more money).

EDIT:
The unit seems rather oversized with 8 kW output in a KFW 55 building, and there is no smaller unit in this series. The heat pump is "fixed speed," so not an inverter system that modulates its output. If you then also install a buffer tank, cycling is preprogrammed.
Overall, a rather price-oriented solution.

Congratulations. You have just completely rendered the concept absurd. First, you pay a 1-1.25% closing fee. Then you invest your money at 0.25% or similar for many years instead of using it to repay your first loan. This is called a negative interest margin transaction. And the "minimum payment" on your outstanding debt will rather be in the range of €1000 upwards per month so that you have a building society savings contract ready for allocation. And lastly, I have not heard of a 1% loan interest rate with building society savers, rather 2-2.5%.

... where exactly did you read the 0.25% p.a.? On the website, the current effective annual interest rate is 1.46% during the loan phase and 0.01% credit interest rate during the savings phase.

I don't want to have read that, but I did. Unlike you, I read it because I went a bit further than just skimming the homepage. In the tariff document under Tariff LBS-Z8 - Interest rate for building loan: 0.25%.