Whatever you might use to make a cheesecake base would suffice for Graham cracker crumbs; it’s quite common to make cheesecake bases with Graham crackers in the US and the taste/consistency should be similar I think…what that might be though, I don’t know

the baking culture in Germany is just a lot different to the American one. We have usually like half the butter/sugar in our recipes, for one. normal cheesecake crusts for us are made with just flour, eggs etc. I will look into it more, though; it’s not like it’s totally unheard to put some kind of crushed cookie into it as well. I’ll just have to check!