Various old manuals downloads in pdf format
 

I found this link - Busse Yachtshop : Datenblätter und Anleitungen on the UK's YBW.com website - thanks to Norman_E.

Most of the manuals are in German, but a great many are also in English.

If in German, there is always the Google translation service. It may be a bit "Chinglish", but will be readable. I have used it a few times.

Well done to Busse-Yachtshop for compiling the list.