Help with heating Radiator on new Apartment

I recently moved to a new flat in Krakow. The flat is new and I’m the first one to move in.
I’m trying turning on the heating radiator from the main room and living room as always but it simply is not workign. It’s not heating anything. I’m moving the valve from level 0 to 5 as I have done I previous apartments.

I’m wondering if there is anything I should do to make it work? The are these 2 levers in these things outside my apartment floor but I’m afraid of moving something I should not do. A friend suggested to look into these but no clue how this works. I tried opening both levers (blue and red labels) and I felt the heating started somewhat to work but turned it off again and set it as it was because I started to hear a bunch of water sounds that I have never heard in any apartment I’ve lived before so not sure if that’s normal on a new apartment.

If anybody can confirm to me which of these to turn on would be appreciated.