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.

But why?
Game of Thrones Season 3, Episode 8

BUT we got out of that,
and we were just...
The Big Bang Theory Season 12, Episode 24

But close enough to pursue him
when he does.
Game of Thrones Season 8, Episode 2

I was excited about my date, BUT turned out
he only asked me because he liked my friend.
The Big Bang Theory Season 8, Episode 8

No, I never doubted you,
BUT others...
Vikings Season 1, Episode 7