The hope of taking over his uncle's business fell through for various reasons. Lehmann returned to Berlin and in 1819 began training as an engraver and lithographer under Johann Gottfried Schadow at the Berlin Academy of Arts. His religious home was initially the Bohemian Lutheran congregation in the in Berlin's Friedrichstadt, of whose preacher he made a portrait engraving. Through his wife Maria Johanna Eleonora, née Eichner, whom he married on 26 October 1827, Lehmann became acquainted with the Moravian Brethren, whose worship life also made a great impression on him. He was active in various revivalist associations, including the ('Main Association for Christian Edification Writings in the Prussian States'), founded by , and as secretary in the temperance association, led by Friedrich Wilhelm Georg Kranichfeld.
