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.

...to ACT like an adult in this marriage.
The Big Bang Theory Season 8, Episode 23

He intends to ACT on this
by not speaking to you...
The Big Bang Theory Season 2, Episode 8

but I do like the idea
that our next ACT of intimacy
The Big Bang Theory Season 11, Episode 10

All right, we have to ACT fast,
before it goes to waste.
Breaking Bad Season 2, Episode 9

I'm not scared.
I don't like the ACT.
The Big Bang Theory Season 12, Episode 10