I really like the music card game Hitster from Jumbo, does anyone know how to print your own cards, which can be read by the official Hitster App?

Here is a Link to the games website so you picture how the game looks if haven't seen it by now. I really like the simplicity of the game but there is a problem, the game comes out of the box with 300 cards and after a few rounds you've heard all of them and the challenge fades away. But the back side of the cards is just a qr code which can only be scanned by the official Hitster App. So I thought some people here probably know more about qr codes than me and maybe have a solution to print more cards. Help is greatly appreciated and I can post additional images if required.