Complex sentence: She officially joined the company on July 15,2005, and was a trainee for over 10 years and was set to debut in the girl group 6mix, prior to competing on "Sixteen".
Split into simpler sentences: She officially joined the company on July 15,2005, and was a trainee for over 10 years. She was set to debut in the girl group 6mix, prior to competing on "Sixteen".