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 knew what would HAPPEN.
Game of Thrones Season 4, Episode 10

It won't HAPPEN again. What's up?
The Big Bang Theory Season 3, Episode 13

liberating a pressure of 40 atmospheres,
not even God knows what can HAPPEN there.
Money Heist Season 3, Episode 4

Now none of that's
gonna HAPPEN.
The Big Bang Theory Season 7, Episode 12

I trust that Penny cares about me
and nothing's gonna HAPPEN with this guy.
The Big Bang Theory Season 6, Episode 8