Hi Dietmar, thanks for your question.
If you subscribe to a Monthly Pro plan you can view your invoices online.
You will also receive a payment receipt via email.
You will be able to print the screen or save as a PDF from your online account.
Please see this link which has instructions on how to do this:
when you pay using PayPal you still pay via Bluesnap so the invoice/receipt will be the same.
The difference between the 12 and 22 EUR option is that the 12 EUR option is paid in one lump sum of 144 EUR (this is a recurring payment that will be taken each year unless cancelled).
The 22 EUR option is paid monthly and is also a recurring payment that can be cancelled at any time.
I hope this clears things up for you.