Jan Kumstat will upset Chun-Hsin Tseng in Prague 2. The match is scheduled for August 22, 2026 and Kumstat brings a 27-13 record for 2026 plus a 17-11 total on the 2026 ATP Challenger circuit, and a 9-5 clay record this season. He defeated Marvin Möller in three sets at the Hamburg Challenger on Au…