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.

I usually don't like LEMON bars,
but these are really good.
The Big Bang Theory Season 8, Episode 6

- Oh, well.
- People say the Soyuz capsule's a LEMON...
The Big Bang Theory Season 6, Episode 5

Howard, I've always thought the LEMON
was an underrated fruit.
The Big Bang Theory Season 6, Episode 5

Shall we have some LEMON cakes?
Game of Thrones Season 3, Episode 2

A LEMON one... or any of them.
Game of Thrones Season 1, Episode 9