Complex sentence: Just Slim's music career started in 2007 as a producer and song writer but made his official debut in December 2010 with is first singles titled "ME" which followed a number of hit singles.
Split into simpler sentences: Just Slim's music career started in 2007 as a producer and song writer. He made his official debut in December 2010 with his first single titled "ME" which followed a number of hit singles.