"Ranking" in Germany depends on the subject you want to focus on in your "management" master.
Accounting: most renowned is the WWU but the program is in German
Finance: Go for Frankfurt, Mannheim strong.
Not a choice by academia but location.
There is no super-strong Finance Master in Germany. If you got the money, try St.Gallen (CH) -competitive!.
Marketing: either Mannheim or WWU (100% English)
Consider WHU (private) for Entrepreneurship
"True" (Organisation, HR, and so on) Management: Go for Mannheim, but there is no real target school in Germany in that field. Mannheim is always a good choice though.
Consider CEMS program Cologne if you want to emphasize your international studies.
But it's really not that important. antworten
I would choose by City and as an international student, Frankfurt may suit you way better than Mannheim.