Complex sentence: She was signed to a recording contract by Decca Records, having her major success with a recording of "I Could Have Danced All Night" in 1956, which sold over one million copies and was awarded a gold disc.
Split into simpler sentences: She was signed to a recording contract by Decca Records, having her major success with a recording of "I Could Have Danced All Night" in 1956. It sold over one million copies, and was awarded a gold disc.