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.

A token of Tyrion Lannister's GOODWILL.
Game of Thrones Season 2, Episode 4

But for that to happen we need
a gesture of GOODWILL from you.
Money Heist Season 1, Episode 11

as a gesture of GOODWILL
from Tyrion Lannister.
Game of Thrones Season 7, Episode 2

But they can withdraw
their GOODWILL at any time.
Vikings Season 1, Episode 1

Because it’s your turn
to show me a gesture of GOODWILL.
Money Heist Season 1, Episode 7