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.

You know, Thor, the god of THUNDER.
The Big Bang Theory Season 8, Episode 18

I'm talking to an orc under the bridge
in Thunder Bluff...
The Big Bang Theory Season 4, Episode 19

Coop and Rolling Thunder
are together again.
The Big Bang Theory Season 6, Episode 6

Thunder.
Game of Thrones Season 3, Episode 9

(THUNDER CRACKLING)
Vikings Season 1, Episode 2