Is the dimensioning of the hot water boiler or heating and ventilation okay?

So if two of us live/shower, the 235l should be sufficient. At 45-47 degrees and 6-9 l / minute, the tank is enough.

Normal shower temperature is 38 degrees. That means if you store 45-degree warm water, it will be mixed down. With your 235l tank, you can easily shower for half an hour. Without considering reheating the warm water.

That's how it looks.

Thank you for your input, I will now use it to initiate the conversation with the [Heizungsbauer].