Question about tolino vision 6

I have installed the OrellFüssli app on my Android phone (or via PC and web browser). What I buy there is automatically synchronised as soon as the Tolino has a WiFi connection. That's how I do it.
I don't quite understand what you mean by "integrated library in German". Of course you can do what you want with hardware, but this is - rather? - an exotic product, so you can't expect much help. Anyway, I've just downloaded Flatland by Abbott directly from tolino via gutenberg.org as EPUB3. And it's now also available to me in offline mode. But I haven't tried to integrate my own digital library yet.

You don't have to buy books. You can also borrow them from a library, which is free. You can also copy PDF documents directly onto it to read. I do this with many manuals, especially for holidays. Of course you can also buy books from exlibris via the integrated browser.