Complex sentence: They advanced to the Oberliga Berlin (IV), which became the NOFV-Oberliga Mitte (IV) in 1991 after the reunification of Germany, where they struggled until being sent down in 1993 after three seasons.
Split into simpler sentences: They advanced to the Oberliga Berlin (IV), which became the NOFV-Oberliga Mitte (IV) in 1991 after the reunification of Germany. They struggled there until being sent down in 1993 after three seasons.