There, his team of Sixten Totzek, Joshua Sutor, Jan-Luca Häg and Till Wunderlich won the bronze medal game, sending them to the 2018 World Junior Curling Championships.

At the championship, the team just missed the playoffs with a 4–5 record after losing their final round robin draw to Canada's Tyler Tardi.

[4] They then lost to Canada's Jacques Gauthier in the semifinal 7–4 and Scotland's James Craik in the bronze medal game 6–5, settling for fourth place.

He competed in his first World Men's Curling Championship that season as alternate for the German National Team skipped by Sixten Totzek.

[8] While attending the Kempten University of Applied Sciences, Harsch returned to world-level curling in 2025, playing in mixed doubles at the 2025 World University Games with teammate Kim Sutor, where they won the silver medal, losing to Great Britain's Robyn Munro and Orrin Carson 10–8 in the final.