It's not my first language, either. And how do you learn? By knowing when you made a mistake and working on it. So now he knows he made a mistake. And can therefore work on it.

gg no re

Edit: since the moron blocked, I have to respond to it here. You're wrong. The comma is correct. But good try.

https://www.pristineword.com/comma-either/#pid=1

Do you get mad at English teachers, too?