First off, I had no idea biker campers were such a big thing in Germany. Across the pond they call them Fahrradwohnwagen and they have grown in popularity in the past few years spawned by the designs of micro-shelter super-designer Paul Elkins.
Paul uses scavenged bike parts and fluted plastic (often from recycled campaign signs) to create hyper-efficient bicycle campers that weigh less than 100 pounds. If you’re interested in recreating one of Paul’s bike campers you can find his plans HERE: