Operate fresh water with partially very high and low buffer temperatures

Yes, exactly like that. A fresh water system is basically just a heat exchanger. The warm water from the buffer heats the cold water from the line in a flow-through process.
If the water from the buffer is no longer warm enough, the fresh water simply makes it as warm as possible.
Completely harmless.

Hello.
Yes, that’s exactly how I thought about it too.
But the reason for the question is as follows.
Since the underfloor heating is practically eliminated now, the buffer tank temperature in summer should actually be lower than in winter. In winter, the heating runs, many people like to bathe a lot. In summer, the heating is off and many tend to shower instead.
In winter, the buffer was always kept at about 65 degrees. Fresh water then produced about 60 degrees.
In summer (so from now on currently), I think 55 degrees in the buffer should be enough.
The fresh water then only produces around 50 degrees, which is completely sufficient for showering, bathing, etc. (it still has to be mixed with cold water).
And the solar system delivers plenty of energy to the buffer during the day, which heats the buffer temperature on sunny days up to about 75 degrees.

Now I just let the temperature in the buffer cool down further until the boiler reheats!
So not like in winter already at 60 degrees buffer temperature, but only at 50 degrees.
That way, the boiler only needs to heat briefly in the morning.
That should be the most economical for the summer months.

I don't see a question there now?

I don't see any question here?

Whether my way of thinking is correct. Lower the buffer tank temperature in summer, let the boiler heat up later, since less energy is needed in the buffer. I also consider maintaining high buffer temperatures in summer (daytime due to solar is clear, but in the evening, at night, early morning) to be a waste of energy. The heating heats the buffer according to the buffer temperature, as the sensor in the buffer is set. Winter = keeping 60 degrees buffer temperature = ok. I think that's too much in summer. In the evening, at night, early morning, 50 degrees would certainly be sufficient.

Yes, it makes sense and is definitely possible without problems. Depending on the situation, you can turn off the heating including hot water preparation yourself, as long as the temperature of the hot water in the morning is still sufficient for you.

Yes, it makes sense and is easily possible. Depending on the situation, you can turn off the heating including hot water preparation yourself, as long as the hot water temperature in the morning is still sufficient for you.

Thank you very much for your help.

So I can leave the setpoint of the fresh water at 58 degrees (circulation at 53 degrees), although sometimes (very early in the morning) the flow from the buffer is only 55 degrees. Then the fresh water just produces around 55 degrees during this time, which is perfectly sufficient. I thought I would have to lower the setpoint of the fresh water as well (e.g. to 52 degrees/circulation 47 degrees).

No, it's fine as it is.