I have learned proprio to mean "just" like in "just around the corner" - proprio dietro l'angolo.
If you just translate it to proper it makes a bit of sense. Proper can mean either suitable (belonging to oneself) or actual (quite) - e.g. "it is the proper cup", or "she has a proper job". Obviously it doesn't translate 1:1, but hopefully that provides some intuition.
Is confusing: 'proprio' can mean 'quite' 'really' or 'truly', from dictionary - different meanings. I said, "It's really good" and got it right!
Context or an indicator. When the sentence doesn't use "Lui" or "Lei," you can assume either, or assume "it."
That's a good rule to follow in general. You will find that some verbs change according to gender and number so you can guess the subject from that. Some adjectives are used strictly for inanimate objects or strictly for living organisms. Here's an example: If the sentence were è proprio bravo then your best choice would certainly be lui because the adjective is used mostly for people and indicates a male subject.
Grazie Ringcycle. What I'm not sure now is about the word 'gentile', do you use it only in a religious context (non- jew) or as synonym of the word nice?
It is definitely not just religious. Gentile also means kind. I remember in one course I took, one of the early phrases was Che gentile da parte sua, which means how kind of you, or how nice of you, which you might say when being invited into someone's house.
Thanks Ringcycle! I did not find an explanation like this on the top 10 Google's results. Tu sei propio carin@. Have a good one!