The temperature in the rooms does not meet our needs

You also have a gas heating system, where it doesn’t matter whether it switches on 10 or 20 times a day. Unlike with a heat pump.

Well, that’s not quite true. Gas heaters also do not like short cycling at all. Sure, they handle it much better than heat pumps, but even here there is eventually an early end.

The balancing was done during construction. We only recently took over the house from the previous owner. Unfortunately, no documentation about the heating was apparently created or it has been lost. Accordingly, the spacing and pipe lengths are unknown.

Regarding the temperatures. In both bathrooms, the temperatures are between 22-23 degrees. Since we basically only use one, 19-20 in the second would be sufficient. The bedroom (18 degrees) and utility room just under 19 are personally too cold for us and we would like 20.

You need a thermal balancing, i.e., a fine tuning. A rough balancing has already been done for you with the hydraulic balancing.

By adjusting the flow rates, your wishes can usually be realized (document everything well!). But be careful, these should only be changed minimally, in steps of 1/4 to 1/3 turns. Under no circumstances start turning wildly because that will ruin the entire balancing and you have to start over, and as you described, you lack the documentation of the current settings.

So either you commission someone who knows about this or try it carefully yourself.

So either you hire someone who knows about it or try it carefully yourself.

That's the problem. Det says without the exact data he can only make assumptions for the calculation. If those are incorrect, then the temperatures still won't match afterwards.

Of course, it would be nice to have the calculations. But they are not necessary. You can simply turn up the flow rate in the rooms that are too cold and turn it down in the rooms that are too warm. Always a little bit and every 3 days you check if it fits (ideally on cloudy days, otherwise solar gains distort your result). Eventually, the setting will be such that you are satisfied

That's the problem. Det says without the exact data he can only make assumptions for the calculation. If those are incorrect, then the temperatures still won't match afterwards.

You can proceed as WilderSueden described. Just turn the room where you need more heat 1/3 of a turn open and the one where you need less heat 1/3 of a turn closed. This way you only change the hydraulics minimally but eventually achieve the desired effects. With underfloor heating, nothing works immediately anyway.

Document everything (temperatures, turns) and wait a few days.

Can one generally say: As long as the spread is low, it is better to increase the flow rate rather than the supply temperature?