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 says it's the next big thing
for social anxiety DISORDER.
The Big Bang Theory Season 4, Episode 22

Excuse me, I have selective mutism,
a recognized medical DISORDER.
The Big Bang Theory Season 3, Episode 6

- And his obsessive-compulsive DISORDER.
- Yeah, that, too.
The Big Bang Theory Season 9, Episode 18

...panic attacks, agoraphobia
and obsessive-compulsive DISORDER."
The Big Bang Theory Season 1, Episode 15

It's what we think caused
your narcissistic-personality DISORDER.
The Big Bang Theory Season 3, Episode 11