“I am neither an expert in design nor am I particularly interested in it,” says Tobias Rehberger. His interactive installations say different. The lumpy, man-high sculptures in this show, for instance—created in Pop Art primaries red, yellow, and blue—take their structural inspiration from termite ventilation towers. Watercolors, diary collages, 3-D paper sculptures, and large prints transform the spaces at Haus am Waldsee, the first Berlin institution to present Rehberger in a solo show. —E.C.