Hello Xaussoghoa40
No, adding tickets that were purchased as a guest cannot be added to the app later. Only tickets and travel cards that were purchased as a registered user can be viewed in the app.
You can present the QR code out of the ticket PDF or right from the purchase confirmation e-mail which was sent to you after each successful purchase.
Please ensure that you bring your physical passport or state ID card (the original document, no paper copy, no photos on your smartphone) along with your ticket. All e-tickets require a proof of identity during ticket inspection.
Best wishes,
Roland