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.

"Do you understand now
why I think you are UNFAIR?
Money Heist Season 1, Episode 9

I bet Jennifer gets a promotion
out of this, which is so UNFAIR,
The Big Bang Theory Season 10, Episode 19

This is cruel and UNFAIR. Cruelly UNFAIR.
Game of Thrones Season 3, Episode 2

This is cruel and UNFAIR. Cruelly UNFAIR.
Game of Thrones Season 3, Episode 2

Don't you think it's a little bit UNFAIR?
Game of Thrones Season 1, Episode 4