You control the temperature in your room with the room thermostat attached to the wall in your own room. You can just leave the radiator knobs in your room set to 5, as the room thermostat controls the temperature. However, you can control the radiators in the hallway and shower room with the radiator knobs.

Are you going away for a longer period of time?
Then set your heating to a lower setting, around 15 ºC is a good option, so it doesn't cool down too much. That way you won't burden the environment unnecessarily.