Complex sentence: Kujan concludes that Keaton actually "was" Keyser Söze; he is convinced that Keaton has faked his death (as he had done some years earlier to escape another investigation) and deliberately left Verbal as a witness.
Split into simpler sentences: Kujan concludes that Keaton actually "was" Keyser Söze. He is convinced that Keaton has faked his death (as he had done some years earlier to escape another investigation) and deliberately left Verbal as a witness.