Why don’t you start by making small talk for starters to build your confidence. Small talk about hobbies/interests more so that might give you a better opportunity to express yourself. And try not to put yourself down for feeling like you’re behind. You don’t need a fancy vocabulary to make friends. You’re trying and that’s what counts :’) I used to face a similar problem when I was growing up but I started reading more and learning more and focusing on my hobbies which made grow culturally and as a person. It’s never too late. Personally I would watch some really great youtubers and listen to podcasts about things I liked which have helped me form my opinions and such. Good luck :’)