Complex sentence: Diane Keaton and Beatty's romantic relationship also began to deteriorate during the filming as Peter Biskind writing about the making of Reds "said," Beatty's relationship with Keaton barely survived the shoot.
Split into simpler sentences: Diane Keaton and Beatty's romantic relationship also began to deteriorate during the filming. As Peter Biskind writing about the making of Reds "said," Beatty's relationship with Keaton barely survived the shoot.