The Frachtschiff-Touristik Kapitän Zylmann GmbH is mediator for the sea voyage and does not book hotels for you.
with a link to  Tourisline you can selct a hotel by your own - and book.

Vaccination: for sailors and passengers of cargo vessels different vaccination provisions from tha tfor noormal tourists may be in effect. See our passage descriptions for information about this.

Maritime books in German language you can order at  Meyers Buchhandlung.