Hope it's okay that I post in English!

I have just moved to Germany and am trying to obtain a German cell phone number/service plan. After looking a various cellular service providers, I decided to sign up for Telekom's  Magenta Mobil Prepaid XL (50 GB) plan with eSIM.  

The problem is that a German phone number is already required to purchase. I do not have a German number, and my USA number is not accepted. Is there any way to sign up for plan first, then use this number on the account?

Thanks in advance for the assistance!