Fortuna came from a goal down to secure a 2-1 victory against their opponent.
Florian Krüger broke the deadlock of the game in the 12th minute to hand Erzgebirge Aue the lead.
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But Düsseldorf clawed back to equalize courtesy Rouwen Hennings’ 45th minute penalty.
With 15 minutes left on the clock, Kasim Nuhu stole the show the match winner as his explosive strike found the back of the net.
Düsseldorf has now progressed to the next stage of the German Cup.
Kassim Nuhu was part of the Black Stars team that played in the 2019 Africa Cup of Nations staged in Egypt.