Who are Ursprungliche Eukaryoten?
It is natural to be confused because the consensus has changed over the years and is still not settled.  In part this is because knowledge has been gained but remains incomplete, and in part it is a matter of opinion and aesthetics about what is best for usefulness at various levels of detail and understanding.

The system put forth in the textbook seems to best match the system Whittaker put forward in 1969.  His Monera is the text's Prokaryota, and his Protista corresponds to the text's Ursprungliche Eukaryoten.  Essentially Protista/Ursprungliche Eukaryoten is a catch-all for all Eukaryotes not included among the Plants, Animals, and Fungi.  There may be some variations in which of the eukaryotic algae are included among the Plants versus the Protista/Ursprungliche Eukaryoten.

It should be noted that in most or all systems of "Kingdoms", at least some of the kingdom groups are not monophyletic, that is, do not include all descendants of a common ancestor, and so do not exactly reflect a true tree of descent.  The Wikipedia Kingdom article notes: 


  Some recent classifications based on modern cladistics have explicitly abandoned the term "kingdom", noting that the traditional kingdoms are not monophyletic, i.e., do not consist of all the descendants of a common ancestor.