Why are the matches hard?

Question

Whenever challenge comes up, its against a higher level person and contains questions from the part I didn't reach yet.
And obviously I lost many times.

Answer 1

You probably need to finish the course before moving to challenges.

Answer 2

Thank you. Although I never mentioned about being obliged to play it.
I was just simply asking to why does it happen? I mean level 6 getting challenged by level 20 with questions out of my known knowledge.

Answer 3

And you are under no obligation to accept the challenge.