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.

was worry and DISAPPOINT them,
Breaking Bad Season 2, Episode 9

and she didn't want
to DISAPPOINT you.
The Big Bang Theory Season 12, Episode 8

You'll DISAPPOINT her before long.
She'll move on.
Game of Thrones Season 6, Episode 4

and they've seen what happens
to men who DISAPPOINT me.
Game of Thrones Season 5, Episode 1

Why would you want to
confuse and DISAPPOINT others?
The Big Bang Theory Season 10, Episode 5