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 don't understand. You were HAPPY
to do this when I hired you.
The Big Bang Theory Season 9, Episode 23

Happy birthday to you
The Big Bang Theory Season 9, Episode 17

I'm not HAPPY about this.
The Big Bang Theory Season 5, Episode 6

Well, they seemed HAPPY and...
The Big Bang Theory Season 8, Episode 7

I just don't think the secret to a HAPPY marriage
is to criticize each other.
The Big Bang Theory Season 8, Episode 9