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.

Go! Go! Follow your COMMANDER!
Game of Thrones Season 6, Episode 9

A letter for you, Lord Commander.
Game of Thrones Season 6, Episode 4

He was the most experienced
COMMANDER in Westeros.
Game of Thrones Season 6, Episode 7

I'm your COMMANDER. Welcome.
Game of Thrones Season 2, Episode 5

And how's that going,
Commander Mormont?
Game of Thrones Season 1, Episode 3