Your sentence is good. I would write "Life is such a great teacher because whenever you don't learn your lesson, he repeats it for you" Notice that I have personified Life by calling it "he". (Say "he" or "she" but don't say "he or she"). That makes sense because you have referred to life as a "teacher", which would be a person. Also, treating it as a person makes it seem like it cares about you.

Looks correct, I see nothing wrong with it!

Yes! Looks great to me.

hello can we practice together?