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.

Anyone named
Desmond Crakehall must be a PERVERT.
Game of Thrones Season 3, Episode 10

Pervert.
The Big Bang Theory Season 7, Episode 7

how long have you been
a demented sex PERVERT?
The Big Bang Theory Season 7, Episode 18

We lost track of
the old PERVERT years ago
Breaking Bad Season 2, Episode 12

he's the PERVERT pulling the strings here.
The Big Bang Theory Season 10, Episode 5