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.

Oh, I love the OBSERVATORY.
The Big Bang Theory Season 11, Episode 10

The Griffith Observatory is
looking for an astrophysicist
The Big Bang Theory Season 11, Episode 10

Please welcome to
the Griffith Observatory
The Big Bang Theory Season 12, Episode 5

at the OBSERVATORY later on,
if you want to join.
The Big Bang Theory Season 11, Episode 8