The Kiev-raised, Berlin-based helmer-writer Sergei Loznitsa (“My Joy,” “In the Fog”) returns to the Cannes competition for the third time in a row with his latest feature, “A Gentle Creature.” What inspired the storyline? I was inspired by Dostoyevsky’s short story “Krotkaya” [“A Gentle Creature”]. It’s about a relationship between a torturer and his victim,...