I get on Facebook and ask PS4 from stranger girls, are they hackers or who is that and how do they hack one?
From Facebook, I have no idea, since I've never been and I do not want to… But on the PS4 you can prevent this by setting up your privacy setting so that not everyone can write to you, but only friends or friends of Friends.
This has absolutely nothing to do with hackers.
https://manuals.playstation.net/document/de/ps4/settings/privacy.html