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.

Too VAGUE.
Game of Thrones Season 3, Episode 6

I try to be as VAGUE as possible,
but I got that guy Victor watching me...
Breaking Bad Season 3, Episode 13

I took advantage
of the VAGUE request
The Big Bang Theory Season 7, Episode 11

He spoke in terms of
a VAGUE investment opportunity.
Breaking Bad Season 4, Episode 8