I told them the exact things: do what’s necessary, yet they keep asked me back: So how can I know what are necessary things? It piss me off, kind of, I really want to help my friends, since they a bit lost themselves into temptations like nightclub, “the game”, love, or video game, etc…

Hey man, not sure what context you mean? What’s necessary to get your life in order, to create your career, to uplift yourself, to stand in line with your values?
You should have a direction you’re going, “what’s necessary” should just be whatever it takes to make that direction as straight and successful as possible – even if your “direction” is your own self development as a man.

Make sure you keep coming back to it – I got given the book as a gift in my teens, and it’s helped me with every setback and crossroads in my life.