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.

DECENCY, concern,
Game of Thrones Season 5, Episode 7

Sergio, if you had to choose between
your DECENCY and your oxygen,
Money Heist Season 3, Episode 4

As soon as DECENCY permits.
Game of Thrones Season 4, Episode 5

You're right. Judas had the DECENCY
to hang himself after what he did.
The Big Bang Theory Season 3, Episode 15

You don't even have the DECENCY to deny it.
Game of Thrones Season 2, Episode 2