Do I have to consider any rules or restrictions regarding the design of the header, description and bullet points in my listing?

Yes, please follow the official guidelines for publishing product information on Amazon.de. See this document for more information:
https://images-na.ssl-images-amazon.com/images/G/03/rainier/help/style/Verkaufsfoerderung_Wohnen_und_Lifestyle._TTH_.pdf