He decided to become a professional poker player during a trip to Canada to play Scoops in May 2014 alongside Reiner Kempe, Fedor Holz, and a few others.
[5] In 2018, Sontheimer won the Caribbean Poker Party $250,000 Super High Roller Championships earning him $3,685,000.
[7] Sontheimer along with Holz is a shareholder of No Limit Gaming, an esports organisation founded by Stefan Schillhabel.
As of August 2020, Sontheimer is 6th on the German all-time money list with career live tournament winnings of over $13,700,000.
He is close friends with many famous German poker players, including Fedor Holz, Stefan Schillhabel and others.