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.

Are you SURE you're ready for this?
Game of Thrones Season 6, Episode 10

And I'll make SURE
the hungry know who's to blame.
Game of Thrones Season 5, Episode 7

Sure, SURE.
The Big Bang Theory Season 9, Episode 11

Sure, SURE.
Thank you very much for the advice.
Money Heist Season 1, Episode 10

Sure, I would be delighted to.
You see, we have been testing
Money Heist Season 1, Episode 9