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.

ENTHUSIASTIC participation
from me regarding my discovery.
The Big Bang Theory Season 7, Episode 10

Subject appears well-rested
and ENTHUSIASTIC.
The Big Bang Theory Season 3, Episode 10

Yes.
In fact, he was quite ENTHUSIASTIC.
The Big Bang Theory Season 2, Episode 23