Complex sentence: Minaj left Full Force, dissatisfied with their lack of success, uploaded songs on her Myspace profile and sent several of her songs to people in the music industry; at the time, she was managed by Debra Antney.
Split into simpler sentences: Minaj left Full Force and uploaded songs on her Myspace profile, sending several of her songs to people in the music industry. At the time, she was managed by Debra Antney.