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.

Mostly with Asian
and Jewish astronauts.
The Big Bang Theory Season 4, Episode 1

I need fennel root for those with fever,
willow bark. Mostly I need milk of the poppy.
Game of Thrones Season 2, Episode 7

But MOSTLY I remember you.
Westworld Season 2, Episode 9

Mostly because I was worried
my mom would walk in.
The Big Bang Theory Season 12, Episode 8

And the therapists in your network
are MOSTLY fine.
Breaking Bad Season 3, Episode 9