

If you suspect you might have sleep apnea, you should first see a doctor. I see you use €, so there’s a chance you won’t need to pay to use a machine - you might get one from your health care operator for free.
For example: my family member in Finland got a diagnosis, and with it he got issued a machine, on the condition that he uses it on most nights. The machine is internet connected. Once a year a doctor makes a remote check-up: they look through the data collected by the machine to see if it works well for you (effective air pressure, persistent obstructions etc.). If you use the machine on most nights (at least 70% of the year), you get to keep it for another year. You also get a new mask, hose and air filter once a year for free.
I hope you can have a similar experience in your home country.
(Forgot to add: I have no idea what the “good enough” CPAP machine costs, it might have to do with the necessary air pressure or other factors i know nothing about. You really should ask your doctor first)

Have you considered that the friends might be insincere about their own frequency too? In many societies masturbation is considered shameful. Even when people admit they do it, they might not want you to think they do it “too much”.