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.

He's FINE.
Money Heist Season 3, Episode 8

Everything is FINE.
Money Heist Season 1, Episode 8

- I'm FINE with that.
- Okay, great.
The Big Bang Theory Season 9, Episode 18

It's FINE.
The Big Bang Theory Season 11, Episode 8

No. Jesse, look. I'm FINE, okay?
Breaking Bad Season 3, Episode 10