Remove parent account on Xbox?

When I got my Xbox One and created an account, something must have gone wrong. The account was taken as a child. So I had to create another "parent" account.

Since this makes handling the Xbox much more difficult, I would like to remove the parent account and set the "child account" as a normal one with all permissions.

Can someone tell me how to do that? I didn't find anything like that in the Xbox settings and on the Microsoft website either.

Write the support times on the website. Or by email.