Deml studied industrial engineering at the Ludwig Maximilian University of Munich.
Chairman WLZ Raiffeisen AG. Chief operating officer Heimstatt Bauspar AG, 1978—1983. Chief Executive Officer Union Investment GmbH, 1983—1988.
Chairman, Chief Executive Officer BayWa AG. President, Chief Executive Officer BayWa Corporation, 1991—2008. Executive officer Austrian Raiffeisen Organization.
Vice president German Raiffeisen Organization. Chairman VK Mühlen AG, since 2004. Member, economic advisory council Bayerische Landesbank, since 2005.
Former board supervisory Man Nutzfahrzeuge AG, Landwirtschaftliche Rentenbank Frankfurt. Former board directors SZVG Süddeutsche Zuckerrübenverwertungs- Genossenschaft eG, Lundenburger Invest Beteiligungs AG. Former vice chairman Rwa Raiffeisen Ware Austria Aktiengesellschaft.
Board supervisory Mannheimer Versicherung AG, Leipnik-Lundenburger Invest Beteiligungs AG. Board directors Warenhandelsgesellschaft m.b.H. Board supervisory Mannheimer AG Holding, Rottach-Egern.
Board directors AGCO Corporation, since 1999.
Since 2011 he served on the Board of Hauck & Aufhauser Kommanditgesellschaft auf Aktien and is a member of the Supervisory Board of the AGCO AG in Atlanta. From 1988 to 2008 he was a member of the board of BayWa AG, since 1991 as Chief Executive Officer Deml was a Vice President of the German - Raiffeisen AG and Chairman of the Austrian-Raiffeisen Landesbanken. He was a contributor member of Lundenburger Invest Beteiligungs AG, Süddeutsche Zuckerrübenverwertungs Cooperative eG to December 2003, Maschinenfabrik Augsburg-Nürnberg Truck & Business Nutzfahrzeuge AG and Landwirtschaftliche Rentenbank, the Bayerische Landesbank and Raiffeisen Ware Austria Aktiengesellschaft.
Since 1999, he supported the supervisory boards of corporations AGCO, VK mills, LeipnikLundenburger Invest Beteiligungs AG, "Our warehouse" Warenhandelsgesellschaft mbH and Mannheimer Versicherung AG. Since 2011 he chairs the Supervisory Board of the Hauck & Aufhauser Kommanditgesellschaft auf Aktien and is a member of the Supervisory Board of the AGCO AG in Atlanta.
Since 2009 he has been a member of the Advisory Board of Halder Beteiligungsberatung GmbH, which he chairs since 2014.