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 will allow you to sign a contract
with your FORMER master.
Game of Thrones Season 4, Episode 10

Between eating and sleeping,
I'd choose the FORMER, but...
Money Heist Season 1, Episode 6

It's Arturo Román.
The Royal Mint's FORMER director.
Money Heist Season 3, Episode 7

Hank and Steve Gomez are working
with a FORMER associate of Walt's,
Breaking Bad Season 5, Episode 14

and murdered
their FORMER friends
Game of Thrones Season 7, Episode 1