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.

- Is that SUFFICIENT?
- Quite. Thank you.
Game of Thrones Season 3, Episode 5

Will that be SUFFICIENT to repair your walls?
Game of Thrones Season 2, Episode 1

...is SUFFICIENT for each person,
as it doubles in volume when cooked.
The Big Bang Theory Season 2, Episode 9

You seem under pressure.
Did I not lend you a SUFFICIENT amount?
The Big Bang Theory Season 2, Episode 14

- And?
- Her accommodations seem SUFFICIENT.
Game of Thrones Season 5, Episode 7