Mens
While a still of junior age, Kapp would be the alternate on the German men's national team at the 2019 and 2023 editions of the European Curling Championships, and the 2022 World Men's Curling Championship.
Kapp would join as the third of the new German team skipped by Marc Muskatewitz during the 2023–24 curling season, alongside junior teammates Felix Messenzehl and Johannes Scheuerl. The new team would have a strong showing at the 2024 World Men's Curling Championships, finishing in 5th place after losing to Italy's Joël Retornaz in the playoffs. However, the team would build upon this success at the 2024 European Curling Championships, they would beat Scotland's Bruce Mouat 9–7 in the final to win Germany's first European medal since 2008, and their first gold since 2004.[2] After winning the European Championships, the team qualified for their first Tier 1 Grand Slam of Curling event, the 2024 National, where they had a strong showing, losing in the quarterfinals to Mike McEwen 6–5. The team also continued to perform well on the world curling circuit, winning the 2024 Karuizawa International Curling Championships. Muskatewtiz would then win the 2025 German Men's Championship against Sixten Totzek, qualifying the Muskatewitz rink to represent Germany at the 2025 World Men's Curling Championship.[3] At the 2025 World's, team Muskatewitz would finish the round robin with a 5–7 record, finishing outside of the playoffs in 8th place. However, the Muskatewitz rink's performance over the last two world championships earned Germany enough points to qualify directly for the 2026 Winter Olympics. There, they would finish in 7th place with a 4–5 record. Team Muskatewitz would finish the season at the 2026 World Men's Curling Championship, where they would again finish outside of the playoffs in 9th place with a 4–8 record. At the end of the season, with Muskatewitz announcing that he will be taking a step back from competitive men's curling due to "personal reasons", Kapp moved up to the skip position of the German men's national team, alongside Messenzehl, Scheuerl, and Mario Trevisiol.[4]