When you register on the course website, you will get a registration email. Reply back to that email (it comes directly to me) with the answer to the following question:
What is your biggest challenge when it comes to Dialogflow?
Note: If your answer is too short, I will ask for some clarifications before I send the coupon. Since it is quite a task to keep track of unexpired coupons, the coupon will have a deadline of a day or two.