I wish when I was 14 I was exposed to more contemporary literature, instead of great classics. And I have no regrets about missing out on math books—most of my friends went to math camp for that kind of knowledge. I'd recommend David Foster Wallace's Infinite Jest; Junot Diaz's This is How You Lose Her; The Collected Stories of Lydia Davis; Haruki Murakami's Colorless Tsukuru Tazaki and His Years of Pilgrimage. I wis…
I'm 25 and I have no understanding of human, sexuality, rich people, old people etc... How do I catch up?
This YouTube series is a good start to how to think about stories: https://m.youtube.com/playlist?list=PL8dPuuaLjXtOeEc9ME62zTf... Actually, John Green's works in general aren't bad for what you are after, but don't restrict yourself to one author.
Accept that not only are all these things maddeningly complex, but that you will never be comfortable with their ambiguity.
Also, go out into the world. Learn to be a good listener so those who are tired, scared, lonely, or otherwise vulnerable will come to you for comfort.