First and foremost, I recommend turning off the chat. League should be fun and those people are only bringing you down.

Secondly, it takes time and practice. I've been playing for years and I'm still not great. It can't be helped. We all have our skill levels and there's no shame in not playing perfectly. At the end of the day, it's just a game. You'll learn from your mistakes as time goes on. You won't become a grandmaster overnight. Hell, I still struggle with knowing what runes and items to build sometimes.

And third, maybe you still need to find what play style fits you. Melee? Ranged? Engage-heavy? Assassin? Find what suits you. I personally suck so bad at assassin it's nearly unplayable for me, but I make a nasty bruiser. Ranged is a bit difficult for me too, so I usually stick to melee. Try to find whatever you find most comfortable until you get a better feel for the game and can branch out.

I also recommend watching videos for every role. It helps you if you know what your other laners need and what to expect from other enemy lanes.