Hi PriomBiswas,
Thank you for reaching out Microsoft Community. We're sorry for the inconvenience this has caused you.
To get the PDF version of your invoice, it would be best to contact support for further assistance. Please check this link https://support.microsoft.com/en-us/help/4051701/global-customer-service-phone-numbers and look for the right number to be able to talk to our customer support in Germany. It's going to be our Microsoft Store Online Support who can handle this concern of yours and if in case you'll be routed to our German Tech Support, there's nothing to worry because they can simply connect you over to the right department.
If this helps, feel free to mark this post as an answer. Otherwise, don't hesitate to respond to this thread if there's anything else that needs to be addressed.
Kind Regards,
Crest_Z