Complex sentence: Sonny calmly stops her, and tells her he made that mistake once and would not make it again, and that her father lied to her (when he said she was not worth loving), and that Sonny loves her and still wants to marry her.
Split into simpler sentences: Sonny calmly stops her, and tells her he made that mistake once and would not make it again. Her father lied to her (when he said she was not worth loving), and Sonny loves her and still wants to marry her.