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.

Even if it turns out you don't have dengue
FEVER, they still let you take a lollipop.
The Big Bang Theory Season 8, Episode 4

A FEVER took him.
Game of Thrones Season 1, Episode 1

One day he was fine, and the next, he caught a FEVER that
Vikings Season 1, Episode 9

I got caught up
in a little wedding FEVER.
The Big Bang Theory Season 5, Episode 23