i have problem with my xbox account

Might be helpful if you told us what the problem is.

i have problem with my xbox accoun

Hi. My name is Brilliant and I am happy to assist you today.

You can try to remove yourself from a family group by:
1. Using a web browser, sign in to family.microsoft.com.
2. Click next to your name and select Leave family group.
3. Select Remove to confirm.

For more details on the above, kindly visit: https://support.microsoft.com/account-billing/leave-family-group-or-remove-members-6d806bbb-eb38-a978-10f4-3bbb814ffcc4

I hope this helps resolve your issue.

If your account is over the age of 18 you must promote it

By removing it from under the control of the parental account

And no changing the ms account nor the age of the acount after the fact won't promote your acciount

It goes by the original dob on your account not future chcanges

Removing it before the age of maturity will only force you back into it by requesting a parental account

Sorry but you must be over the age of a minor as defined by the country you are in. Also if you are an adult and you age is correct on your account the other reason I've found is that your account is managed by a family parent account. If this is the case
then your will always be considered a child account as this is what they are considered no mater your age.