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.

You swore to OBEY me.
Game of Thrones Season 1, Episode 10

Will you OBEY now?
Game of Thrones Season 1, Episode 10

But for now, shut your mouth and OBEY,
or I will make another heir who will.
Game of Thrones Season 6, Episode 2

When he commands, we OBEY.
Game of Thrones Season 3, Episode 7

Wars teach people to OBEY the sword,
not the gods.
Game of Thrones Season 5, Episode 4