Previously, he wrote as a freelance journalist for daily newspapers such as Frankfurter Allgemeine Zeitung and Die Welt and worked as a documentary filmmaker for national German television ZDF, mainly focusing on history and present of the Arab world.

[1] In 2014 he co-founded Candid Foundation, a privately chartered, independent think tank which devotes itself to international and intercultural cooperation and implements media and technology driven projects with countries of the Mediterranean, Middle East, West Asia and the Caucasus.

[2] Among his co-founders were the political scientist Asiem El Difraoui, social entrepreneur Belabbes Benkredda, and the photographer and documentary film director Marcel Mettelsiefen.

Gerlach is a frequent guest expert with German and international news broadcasters where he comments on Syria, Iraq, the Arab world and European-Arab relations.

He argues that the essential core of Syrian government was not simply a group of people around the Assad family, but a distinct logic of thinking and behaviour, an ideology described as implicitly sectarian.

[22][23][24] This analysis was corroborated in 2020 by news media reports stating that Saudi crown prince Mohammed bin Salman had secretly encouraged Russia to intervene and, in this way, "angered" CIA director John Brennan.