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.

the way you feel when you’ve just
had the best shag of the CENTURY.
Money Heist Season 1, Episode 12

the last dragon had died a CENTURY ago.
Game of Thrones Season 6, Episode 2

Fine. How about one of the most beguiling
and influential couples of the 20th CENTURY?
The Big Bang Theory Season 6, Episode 5

...was a third CENTURY Roman priest
who was stoned and beheaded...
The Big Bang Theory Season 3, Episode 15

Thailand has had the fork
since the latter half of the 19th CENTURY.
The Big Bang Theory Season 1, Episode 2