I wanna be expert in english

I am 14 year old non-native english speaker.I wanna be expert in english within a few time.I don't wanna study grammar cause I am expert in it.I also know must of the vocabulary,idioms,phrases,expressions etc used in daily english but not all.At least I wanna be like native english speaker.

Also,I fell very difficult to understand to British speakers.Its not that hard to understand to American english.Can anyone suggest me any solution.I would be really pleased if there are any effective websites to learn english free online

just keep practising maybe you can join some clubs after school to socialise with oather kids.