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.

that you're fundamentally unlovable
and THEREFORE going to be alone forever.
The Big Bang Theory Season 10, Episode 22

They matter to my buyer in the Czech
Republic, THEREFORE, they matter to me.
Breaking Bad Season 5, Episode 10

We are traveling together
in each other's company, THEREFORE...
Game of Thrones Season 5, Episode 6

Therefore, according to
the transitive property,
The Big Bang Theory Season 12, Episode 8

Therefore, I want to...
Money Heist Season 1, Episode 8