Inside the house 10° warmer than outside - how does that happen?

Regarding the actual temperature: With us, if the room temperature sensor is missing, the heating assumes the room setpoint temperature = ACTUAL. If it is the same for you, you can adjust as you like and adapt to reality.

The room setpoint temperature plays a role in the heating curve, so you should not just adjust it arbitrarily.

In the summer, the heating curve is a bit off for me though ;) You can just set it back to the fixed value for the heating period.

In tennis, you cannot just raise the net higher for your opponent. With your house, you cannot activate the insulation effect only for the winter. Heat that enters the house simply stays inside longer. Without shading, the sun heats the materials it reaches through the glass. These then emit heat, which stays inside the house. The same applies for sunny days with hot outside air and open windows and doors. Once the warm air is inside the house and heats the materials inside, it takes time to get the heat out again. So, two principles help:

[*]Do not let heat into the house. There are 3 measures for this: Avoid direct sunlight through windows = shading and do not let hot air in = keep openings closed, turn off the heating.
[*]Provide active cooling

The stronger the insulation, the slower the system. That is the difference to your house from 1982.

In summer, however, the heating curve is a bit off ;) You can always set it back to a fixed value for the heating period.

And what sense is that supposed to make? You set the room setpoint to the current room temperature of 23 degrees, then the sun shines and the temperature in the living room rises and you run back to the heat pump and set the new temperature so that the value matches the current room temperature?

..,
Without shading, the sun heats the materials it reaches through the glass. These then radiate heat, which stays inside the house.
…

Therefore, praise for electric roller shutters (or similar) with a sun sensor. These close to 80%. This keeps out the majority of the heat while still letting in enough light.