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.

Oh, boy, it is CRAZY
in here tonight, huh, Glenn?
The Big Bang Theory Season 9, Episode 15

it sounds CRAZY, but it
really works; ask Leonard.
The Big Bang Theory Season 12, Episode 19

CRAZY face.
The Big Bang Theory Season 5, Episode 17

This road trip just got CRAZY. Ha, ha.
The Big Bang Theory Season 8, Episode 19

And you're fucking CRAZY,
but you haven't headbutted me yet.
Money Heist Season 3, Episode 8