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

He's the Lord of Riverrun.
I have to OBEY his commands.
Game of Thrones Season 6, Episode 8

To OBEY.
Westworld Season 3, Episode 8

What you command, we will OBEY.
Game of Thrones Season 8, Episode 4

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