I think that Google recently made a policy change that they will always use your Gmail as your Google account and any associated emails will just "redirect" to your Google account. So when you log in with your
yahoo.de tied to your Google account, Google hands us back the @
gmail.com address associated with your account. Since App Inventor keys off of your email address, this results in us creating a new account for your @
gmail.com, which will be empty. If you email me from both your
yahoo.de and
gmail.com accounts, I can migrate your projects for you.