Regarding the USB modem including SIM card, you'll find information at
Tchibo - Internet Stick inkl. Prepaid SIM-Karte
However for regular Tchibo SIM cards purchased separtely (without USB modem) data options are not officially available. So don't expect Tchibo to confirm any of the infos in the linked article, which btw was written by me. But believe me, it works flawlessly - I've several friends, who use Tchibo's data options with a regular SIM card.