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.

if you KNOW what I mean.
The Big Bang Theory Season 11, Episode 8

She doesn't KNOW
what she's talking about.
The Big Bang Theory Season 12, Episode 8

Aye, I did KNOW.
Game of Thrones Season 4, Episode 7

LOTHBROK:
They KNOW we're here.
Vikings Season 1, Episode 2

Do you KNOW how long l had it?
Fifteen hours.
Breaking Bad Season 4, Episode 7