Lehmann grew up in Troisdorf in the Rhein-Sieg district in then-West Germany. In 1999 he graduated from the Gymnasium zum Altenforst in Troisdorf. In 1999 he began his studies of political science, Romance studies and education in Cologne and Aix-en-Provence, which he completed in 2006 as Magister Artium (M.A.).
From 2005 to 2007 Lehmann headed the constituency office of Kerstin Müller, a member of the Bundestag in Cologne. From 2007 he worked for the Rhineland Regional Council, most recently in occupational health management.
Political career
From 2010 to 2018, Lehmann served as co-chair of the Green Party in North Rhine-Westphalia, alongside Monika Düker (2010–2014) and Mona Neubaur (2014–2018).[4][5]
Lehmann became a member of the Bundestag in the 2017 German federal election, representing the Cologne II district.[6] From 2018 until 2021, he was a member of the Committee on Labour and Social Affairs.[7] He also served as his parliamentary group’s spokesman for queer politics and for social policy.[8] Within his parliamentary group, coordinated the Trade Union and Social Advisory Council.
In a podcast interview on online dating Lehmann remarked how actively Grindr was being used during parliament sessions, and how it relates to his work.[15]