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.

I had no IDEA how to make her happy,
Game of Thrones Season 2, Episode 2

- Maybe you guys can run together.
- That's an excellent IDEA.
The Big Bang Theory Season 4, Episode 2

Maybe Euron Greyjoy
had the right IDEA.
Game of Thrones Season 7, Episode 7

At best you can say, "Hey, look, my IDEA
has an internal logical consistency."
The Big Bang Theory Season 1, Episode 3

You have any IDEA how that feels?
The Big Bang Theory Season 10, Episode 6