The best way to learn proper English is to read news report, and watch news on TV. Watching TV shows is a great way to learn casual English, slang words, understand culture reference and humor. If you have already watched these shows then you may recall the words used in the following dialogs.

I thought you LEFT a long time ago.
The Big Bang Theory Season 6, Episode 8

Oh, my God, you still go LEFT!
The Big Bang Theory Season 7, Episode 4

I'm the only vote LEFT...
Breaking Bad Season 5, Episode 8

And if there's anything LEFT of you,
Game of Thrones Season 6, Episode 4

And when she LEFT, did you open it?
Money Heist Season 1, Episode 7