Simplify the following text for a Grade 13 native English-speaking person.
Original: He spent much of his time from the 1950s onward in Germany as music director of the Bavarian State Opera ( 1956 â `` 1958 ) and as conductor of the RIAS Symphony Orchestra , the Deutsche Oper Berlin and the Berlin Philharmonic .
Simplified: He spent much of his time from the 1950s onward in Germany as conductor of the Bavarian State Opera ( 1956 â `` 1958 ) , the RIAS Symphony Orchestra ) ) , the Deutsche Oper Berlin and the Berlin Philharmonic .