Sonnekalb represented Germany at the 2024 Winter Youth Olympics. On 22 January 2024, during the first day of the speed skating events, he won a gold medal in the 500 metres with a time of 36.61. The next day he won a gold medal in the 1500 metres with a time of 1:50.53. On 26 January, during the final day of the speed skating events, he won a gold medal in the mass start with a time of 5:30.07.[1][2] He competed at the 2025 World Junior Speed Skating Championships and won gold in the 1000 metres, 1500 metres and overll event. He became the first German to win the World Junior Speed Skating Championships overall title since Michael Spielmann in 1988.[3]
During the first World Cup event of the 2025–26 ISU Speed Skating World Cup on 15 November 2025, he earned his first career senior World Cup podium finish, finishing in third place with a World junior and German record time of 1:41.33.[4][5] During the second World Cup event a week later on 22 November 2025, he finished in second place in the 1500 metres with a time of 1:42.31, trailing only Jordan Stolz.[6]
On 20 January 2026, he was selected to represent Germany at the 2026 Winter Olympics. He finished qualification ranked fourth in the 1500 metres and fifth in the 1000 metres standings.[7] During the Olympics he finished in 12th place in the 1000 metres and 13th place in the 1500 metres.[8] He then competed at the 2026 World Junior Speed Skating Championships and won gold medals in the 500 metres, 1000 metres, and 1500 metres, and defended his overall title from 2025.[9]
