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.

we deem likely to be SUCCESSFUL.
Game of Thrones Season 7, Episode 3

because he's hopeful
for a SUCCESSFUL military alliance.
Game of Thrones Season 7, Episode 6

But if our story is that
the car wash is SUCCESSFUL,
Breaking Bad Season 5, Episode 9

Well, now you get to go back
as a SUCCESSFUL scientist.
The Big Bang Theory Season 8, Episode 22

...whose last SUCCESSFUL experiment
was lighting his own farts.
The Big Bang Theory Season 1, Episode 4