It’s always interesting to see what an actor will deliver as they make the step towards directing, and for “Next Door” director and star Daniel Brühl has not shied away from a premise that closely parallels, yet distorts, his own life. It’s a film that explores a space of conversation highlighted to great effect in Bong Joon-ho’s recent towering success, “Parasite,” toying with societal dichotomies and opening up discussions around wealth, class, gentrification, and spatial divides. But where “Parasite” was ominously slick and raucous, “Next Door” is muted and stifled.