you have to call the Kustomer-Service, because if you have no german ID, there is only one way to verify your age --> the postal way.
You will get a Customernumber with the registration-confirmation email, if you did not recieve it you can try it with this link:
I hope this could help you.
I don't have a registration-confirmation email because I couldn't register because I don't have a german ID.
Also the link you've provided doesn't help - I've tried that 3 times and didn't receive any email.
I think it's because I didn't finish my registration which I couldn't because of the age validation.
What should I do then?