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.

Theon holds the castle with a SKELETON crew.
Game of Thrones Season 2, Episode 6

whose SKELETON sits
on the Iron Throne.
Game of Thrones Season 7, Episode 3

Skeleton with phosphorous
on a zip line.
The Big Bang Theory Season 5, Episode 7

I assure you a madman
is scarier than a SKELETON.
Money Heist Season 1, Episode 1

Unless they develop technology
to fuse my SKELETON...
The Big Bang Theory Season 2, Episode 14