Immowelt promotes Björn Sass to MD by Johanna Wild in Insiders, Real Estate 04 Dec 2018 Immowelt Hamburg GmbH has promoted its former head of M&A and Investments Björn Sass to managing director. The appointment was made in August but was only recently announced. This article is only available to AIM Group clients. Please subscribe now or log in to view. Share Björn SassImmowelt Hamburg GmbH Johanna Wild Johanna Wild is our writer/analyst for Germany, Switzerland and Austria.