First he learned, assisted by Carlo Bohländer, playing guitar and since the mid-1950s, he played jazz in the clubs of the U.S. Army. During the 1959/1960 national service, he switched to the bass. 1961 Albert Mangelsdorff picked him up as member of the Albert Mangelsdorff Quintet. Since then Lenz has also become a member of the "hr-jazz ensemble," for which he arranged and composed too. In 1965 he worked in the quintet of Krzysztof Komeda, taking part in the recording of the album Astigmatic. In 1968 he played with Joachim Kühn and Aldo Romano in a band led by Barney Wilen at the Berlin Jazz Days. 1970, he played with the George Russell Sextet, and also with a band led by Leon Thomas. 1972 Günter Lenz played with Lightning Hopkins. This allowed him to collect big band experience.