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.

Are you under the IMPRESSION
that we're still friends?
The Big Bang Theory Season 3, Episode 6

I wasn't under the IMPRESSION
you liked him very much.
Game of Thrones Season 8, Episode 2

It will also help improve
her initial IMPRESSION of you.
The Big Bang Theory Season 4, Episode 5

Were you under the IMPRESSION that
Leonard has no complaints about you?
The Big Bang Theory Season 3, Episode 7