I am over 25 and have a half-fare travel card. Can I continue to pay the «Young Adult» price for the ZVV 1-month travelcard?

No. Our travelcards are already subject to very considerable discounts. Therefore further discounts via the half/fare travelcard cannot be awarded. We do recommend you to purchase an annual travelcard: In comparison with the monthly travelcard you would be travelling over 20% cheaper.