When it became clear I realized something was wrong with the water in my apartment.
There was low pressure, and the boiler was giving very slow heating.
I contacted repair services, but everyone gave different explanations — boiler.
I decided to разобраться it myself. That’s how I found this website: https://stroyka2001.kh.ua
There they clearly explain causes of low pressure.
After reading a few articles, I understood why previous repairs didn’t help.
I advise paying attention to it to anyone who wants to save money on repairs.