That sounds incredibly frustrating.  I wish I could help.

KA has a small staff, and I don't know how long it would take for them to see this post. In my experience, the posts to Support Community are usually about issues that are not urgent, and that can benefit from input or discussion with other users.  (I don't think it's likely that other users can help with your problem.)

You might get a faster response from KA staff by using Report a Problem.  Or it might be faster to start the course challenge over, if that is a possibility (I have never done a course challenge).

SaraNazish

What course is this? the coding modules normally have a "start over" button at the bottom of the coding window. 

It s 6th grade math

And no, it does not have a start over button.

And if you're a perfectionist, you know how frustrating this is.

Hi SaraNazish,

I completely understand how distressing this situation must be, and I want to assure you that I empathize with your concerns. However, I must clarify that we currently cannot manually re-adjust Course Mastery Levels after achieving an undesired result in a Course Challenge. This is a policy in place to maintain the integrity of our assessment system.
 
To regain your mastery progress in the particular skills you leveled down and achieve 100% mastery in the course, you will need to retake mixed-skill assessments. I highly recommend opting for unit tests, as they generally cover less content and include fewer questions compared to a course challenge, making it a more manageable option for you.

Concerning the "Start Over" button for Course Challenges, I have forwarded your feedback to the team. It will be considered in our discussions about the future of Khan Academy.

I know this may not be the response you were hoping for, but I appreciate your patience and understanding.

Sincerely,

Fernando