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.

As totally PRODUCTIVE.
Breaking Bad Season 2, Episode 3

My friendship
with the Lannisters was PRODUCTIVE.
Game of Thrones Season 4, Episode 4

Take a step toward
a more PRODUCTIVE relationship
Game of Thrones Season 7, Episode 3

You're searching for some other area
where you can feel valuable and PRODUCTIVE.
The Big Bang Theory Season 1, Episode 12

You were right.
This was a very PRODUCTIVE evening.
The Big Bang Theory Season 4, Episode 1