Complex sentence: During the 2015 playoffs, Portland won the Western Conference final, their first postseason trophy, and advanced to MLS Cup 2015, which they won 2--1 against the Columbus Crew.
Split into simpler sentences: During the 2015 playoffs, Portland won the Western Conference final, their first postseason trophy, and advanced to the MLS Cup Final. In 2015 they advanced to the final stage of the playoffs, the 2015 MLS Cup, winning 2--1 against the Columbus Crew.