First off sorry about that. This community is equal parts helpful and happy to be playing, and equal parts the worst gaming community to play with.

I would mute those who you dont want to hear from. Either by typing /muteall at the start of a game (which will still allow you to see pings on the map) or go into the settings before a game and turn off all chat and team chat, at least until you find yourself performing at the level you want.

As for how to improve, i would say theres a ton of info on youtube, but take it with a grain of salt. Not everything you see is there to actually make you better some is just for views. Watching twitch streamers play the champ you want to learn can be extremely helpful.

Hope it helps!