Jugendschutzeinstellungen beenden ohne das google konto zu löschen?

Google will normally give instructions seven days ~after~ the child reaches legal age. You can however act before those arrive. 

Just be aware, that if the child is not the legal age in your country, https://support.google.com/accounts/answer/1350409, and you remove the child from Family Link, then Google will be obliged to close the account, with usually no chance of recovery. Everything in the account will be lost.

To remove supervision on the child's account, please try these steps below:

The Family Link supervisor to open an incognito window or private browser then sign-in to your child's account.

Open another incognito tab then go to families.google.com/graduation.

Read the terms of service then select "I'm ready".

If that doesn't help, please contact the Family Link team using, for Chat Support:- https://support.google.com/families/contact/chat_new  or Email Support:- https://support.google.com/families/contact/email_new. 

If those links don't work (sometimes in some countries they don't), try  https://support.google.com/families/gethelp

Family Link FAQs https://families.google.com/familylink/faq/

Google for Families Help Centre https://support.google.com/families

https://support.google.com/accounts/thread/253329502/want-to-change-child-s-account-to-adult-account?hl=en