My girlfriend created a netflix account where she entered me 12 even though I'm 19 years old, how can I change that, and can I change that at all?
Create your own Netflix account? If you have a profile for you in her account: she could edit that and change her age if she wanted to. Others can do very little there.
So, as it is so beautiful on the Internet:
After creating a Netflix profile, you can edit it even further and rename the Netflix profile, for example, by tapping the profile picture or the app version in the "Edit" section. Then, for example, the default language, age rating, name or profile picture can be changed. Age ratings include "All ages," "For teens and below," "For older children and below," and "Only for small children." Unfortunately, only the default 15 images are available in the profile photo - you can't add your own photos.
https://www.turn-on.de/primetime/ratgeber/netflix-profile-loeschen-hinzufuegen-und-bearbeiten-so-gehts-343045
OK thanks
