PLEASE ADD A RESET BUTTON FOR THE COURSE CHALLENGE

I've spent MONTHS on a course and all my work was washed away with a course challenge, i am so upset, its like I wasted 5 months on a course and it didn't matter at all. I'm begging, please let me reset it, I've attempted the course challenge 9 more times, but it hasn't been making a difference. I'm tempted to delete my account and spent another 5 months trying again or just quitting Khan academy altogether. Please, this has caused me so much pain and agony.