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.

Not NECESSARILY.
The Big Bang Theory Season 10, Episode 17

Not NECESSARILY.
I think
The Big Bang Theory Season 5, Episode 20

Not NECESSARILY. I'm often surprised
by my lack of familiarity with Leonard.
The Big Bang Theory Season 1, Episode 17

I'm not NECESSARILY talking to the food.
The Big Bang Theory Season 2, Episode 4

...if the cafeteria NECESSARILY qualifies
as being part of the hospital.
Breaking Bad Season 3, Episode 8