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.

Ten seconds after I tell this story,
I'm a CIVILIAN.
Breaking Bad Season 5, Episode 10

"A CIVILIAN is going towards
the command post, he's with Almansa.
Money Heist Season 1, Episode 4

Hey, I'm a CIVILIAN.
I'm not your lawyer anymore.
Breaking Bad Season 5, Episode 15

But in case of doubt, we assume
there can be CIVILIAN victims.
Money Heist Season 3, Episode 6