From 2009 to 2015 he studied electrical engineering and information technology at the Technical University of Munich, where he received a master of science.
[2] From 2009 to 2012 he worked as a manufacturing engineer at Tridonic GmbH & Co KG in Austria and the United Kingdom, and then at ThyssenKrupp Presta AG in Eschen from 2015 to 2019.
Since 2021, he has worked as a technology development engineer at Ivoclar in Schaan.
[2] In November 2021, he was the only member of the Landtag to speak out against the establishment of a low-threshold drug-addiction counseling center in Liechtenstein and early drug-addiction prevention in schools.
[3] Shortly after the founding of the Mensch im Mittelpunkt in January 2022, Gassner occupied the URL menschimmittelpunkt.li from the party, and then he later sold it, donating the proceeds to the Liechtenstein state hospital.