Lang was regarded as an influential director, especially known for productions of works from the German classical period by Goethe, Schiller, Lessing and Kleist among others, with "a new, authentic approach".

[3][5][6] During his final year of study, Lang was the narrator in the play Der Schuhu und die fliegende Prinzessin by Peter Hacks.

[4] His first major role there was Ferdinand in Schiller's Kabale und Liebe in 1972,[6] and his pure unconditional passion divided the critics; some were enthusiastic while others thought that after Brecht, emotions on stage were embarassingly private.

[6] He played the title role in Kleist's Der Prinz von Homburg in 1975, which was regarded as an extroardiny portrayal of a Prussion officer who misses happiness for duty, directed by Andreas Dresen.

[6][4] He appeared in the title role in the monumental production of Goethe's Faust II, staged in 1983 by Friedo Solter [de], alongside Dieter Mann as Mephisto.

[8][9] Lang's film and television appearances were relatively infrequent, including a prominent role, the philosopher Ralph in Konrad Wolf's 1980 film Solo Sunny, alongside Krößner,[5] and the title role in Peter Vogel [de]'s television adaptation of Stephan Hermlin's short story Der Leutnant Yorck von Wartenburg in 1981.

[6] After Dieter Mann became director of the theatre in 1984,[8] Lang directed Goethe's Iphigenie auf Tauris, with Paryla in the title role, and Grabbe's Herzog Theodor von Gothland [de], with Grashof in the title role, that year, Johannes R. Becher's Winterschlacht with Mann in 1985, and a Trilogy of Passion consisting of Medea by Euripides, Goethe's Stella and Strindberg's Totentanz in 1986.

[2] He was simultaneously, with Alfred Kirchner, Volkmar Clauß and Vera Sturm, a co-director of the National Drama Theatre [de] in East Berlin.

[2] He staged at the Schillertheater in 1989 Bernhard Minetti's Märchen in Deutschland based on fairy-tales of the Brothers Grimm as well as Schiller's Die Räuber.

The following year, when Berlin was unified again, he presented a new production of Goethe's Iphigenie auf Tauris and another of Molière's Der eingebildete Kranke.

[2] Lang received the Konrad Wolf Prize from the Academy of Arts in 2020;[10][1] The jury acknowledged his work, beginning as a spectacular young protagonist and then directing classical plays in "a new, authentic approach" with his "close-knit ensemble", inspiring with "comedic wit and enlightening fantasy".