Termet Furnace Failure: Error E09, Pressure 3.7 Bar - Troubleshooting & Quick Help Needed

Welcome,
I would like to ask for quick help. We have the second day of Christmas and my oven broke down. Error E9 is displayed and pressure 3.7 bar is indicated. Sometimes the furnace caught 'failures' when the pressure was too low and you had to unscrew the valve for a while.
I have no idea how to deal with it, and the apartment is getting colder.
Adds some preview photos. I am asking for quick help.
Added after 51 [seconds]:

The manual says what is this error !! Too low or too high pressure. It should be in the range of 0.5 to 2.5 bar. Drop water from the central heating installation. If the pressure continues 3.7 bar, it indicates a damaged pressure transducer. By the way, a diaphragm vessel to be checked.

Can you tell me how to do this? Is this one of the valves at the boiler? Forgive me, but I'm green in it.

Drain the radiator through a manual vent. However, I suspect a damaged transducer. Normally at 3 bar the safety valve should open and release excess pressure.

Check the operation of the safety valve in the boiler. Before you can also drop the water pressure in the installation

Please help.
I use the TERMET boiler in an open system with a fireplace. The factory-set working pressure in the boiler is 0.5-2.7 bar. The problem is that the height of the water column gives me a pressure of 0.4 bar. At this pressure, the boiler will not start. I need to close the valves on the fireplace and make up the pressure above 0.5 bar. I would like to set a minimum working pressure of 0.3 bar. How to enter service settings and what parameter to change. I know that a service technician can do it, but as other users write, it costs about PLN 100-150, and besides, I asked for it during the assembly of the boiler two years ago but he refused me. If I reduced the working pressure, I wouldn't have to fan the fireplace valves, which would one day refuse me, and besides, I manage, but my wife doesn't really.

There is no such thing as the ability to change the minimum pressure.

I called the manufacturer's website and they said that a service technician could do it, so it is possible.

In such cases - when holidays and cold - light the fireplace?
Others also have holidays and do not bother them with your troubles resulting from mediocrity and the furnace and the implementation of the arrangement

This kind of talk pisses me off. He has a job, let him work. I call the 'foremen' and all the time after the visit something is wrong. If they work on their heads, let them come even in the evening on Christmas Eve. I don't feel sorry for them one bit. After all, they are overpriced for it.

Ukarz me! 😆