how to change birthday with family settings

Hello there! Regarding your explanation, I believe you will need to follow the instructions on this link and your issue should be resolved.

How to change a birth date on a Microsoft account

It should automatically get changed in to an adult account on the birthday or the day after the birthday. But it would be still in family settings.

As said it should change over on your birthday. I would check and adjust your settings in the family settings 👍

In all honesty, it depends how old you are. If you made this account set up as a young birthday, then the chances are you cannot download it. However you may change your settings via Family Settings, or have your adult set up a parent account and enable
the use of certain games.

~AGS Defeats

Even not being in a Microsoft Account Family, if the birth date on your Microsoft Account makes you a minor in your region, then it will default certain settings for your account so that Microsoft can cover legal liabilities, and to make those changes you
would need to be in a Family and have an adult account in that family make changes for your Privacy and Online Safety Settings.

Simply removing yourself from a Family Account does not release the restrictions set for a Child account.

So you would either A) have an adult account add you to their Microsoft Family and make the Privacy and Online Safety Settings or B) if your account birth day is wrong and you don't think you should be a child based on your actual birthday, then you can
change the birthday on your account to reflect your real birthday, and
then perform the Age Verification Process.