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.

and a GENTLEMAN of honor.
The Big Bang Theory Season 11, Episode 12

Will the GENTLEMAN from the great
state of denial yield for a question?
The Big Bang Theory Season 1, Episode 13

Leonard, do you not recall the last time
we visited this GENTLEMAN?
The Big Bang Theory Season 2, Episode 14

It's from the GENTLEMAN
at the end of the bar.
The Big Bang Theory Season 12, Episode 12

I'm a GENTLEMAN,
I wouldn't allow that to happen.
Money Heist Season 1, Episode 6