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.

Well, I had just begun PUBERTY...
The Big Bang Theory Season 8, Episode 23

but that will work better
after Sheldon hits PUBERTY.
The Big Bang Theory Season 5, Episode 19

Oh, yeah, back before he hit PUBERTY
and grew man parts.
The Big Bang Theory Season 10, Episode 24