Original: Then Walter returned in 1900 to Berlin, where he assumed the post of Royal Prussian Conductor at the Staatsoper Unter den Linden, succeeding Franz Schalk; his colleagues there included Richard Strauss and Karl Muck.
Simplified: He then went to Riga, returning to Berlin in 1900 where he conducted at the Staatsoper Unter den Linden where he worked with famous people such as Richard Strauss and Karl Muck.