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.

Which brings us back to
that hulking SIMPLETON over there.
The Big Bang Theory Season 10, Episode 9

A crippled boy being pulled on a sledge
by a SIMPLETON?
Game of Thrones Season 4, Episode 4

a good-natured SIMPLETON
like Penny is that
The Big Bang Theory Season 5, Episode 13