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.

Dereliction of duty in the face of
the enemy is a court-martial OFFENSE.
The Big Bang Theory Season 2, Episode 16

N-No, you can't be.
I said "no OFFENSE."
The Big Bang Theory Season 12, Episode 17

that would have
given her OFFENSE.
The Big Bang Theory Season 12, Episode 22

I'm not. No OFFENSE.
The Big Bang Theory Season 1, Episode 6

Hank, no OFFENSE,
but l think you're
really reaching.
Breaking Bad Season 4, Episode 7