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.

'Cause Leonard was FAT.
The Big Bang Theory Season 7, Episode 11

Your mother was
a dumb whore with a FAT arse.
Game of Thrones Season 1, Episode 5

A mic hidden in the FAT tissue,
in the skull, anywhere.
Money Heist Season 3, Episode 7

No! No, come on. Come on,
you're not gonna get FAT,
The Big Bang Theory Season 9, Episode 16

...and the use of her George Foreman Grill
that seals in the flavor without the FAT.
The Big Bang Theory Season 4, Episode 1