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.

He was SUFFERING.
Breaking Bad Season 4, Episode 7

A lot of people are SUFFERING.
What do you plan to do?
Money Heist Season 1, Episode 4

who's used to SUFFERING
and unpleasant smells.
The Big Bang Theory Season 7, Episode 23

We're standing in the hallway,
SUFFERING through an awkward encounter.
The Big Bang Theory Season 3, Episode 7

Raj, now, I'm sorry you're SUFFERING.
The Big Bang Theory Season 9, Episode 15