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.

Drink long and DEEP, my noble king,
Game of Thrones Season 6, Episode 6

Not to mention that the snow is so DEEP,
Game of Thrones Season 5, Episode 8

- It's not DEEP.
- I thought they were going to kill me.
Game of Thrones Season 2, Episode 6

(IN DEEP VOICE)
\"What are you doing in our dungeon?\"
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(IN DEEP VOICE)
\"What are you doing in our dungeon?\"
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(IN DEEP VOICE)
"What are you doing in our dungeon?"
The Big Bang Theory Season 6, Episode 23

It's peaceful and DEEP.
The Big Bang Theory Season 10, Episode 13