facebook is able to determine who you interact with irl with things such as:
geolocating: (where you check in, and gps on your phone and computer)
IP addresses: (the digital address your computer has, they give rough locations to where you are, a lot of computers share these addresses)
what school and workplace you go to
photos: (if you upload a photo, it will suggest people who have you in their photos)
workplaces, schools, events etc (pretty self explanatory)
and phone contact lists.
FB recommended friends can be eerily accurate because of this (i’ve had long distance friends secret profiles, that I’ve known about but not seen, with no friends in common at all, not even a photo was up, recommended to me)
FB or the people recommended are not stalking or targetting you, this is how FB works.
if you need to hide:
there are settings to hide your profile, use them. check reccomended friends, block people you don’t want to see. don’t add schools or workplaces, don’t attend events, don’t check into places, turn gps off on your computer and your phone. don’t put photos up, and definitely don’t tag them. proxies and vpns can hide your IP, i think (double check this)