Donyell Mallen scored a brace as Borussia Dortmund claimed a 4-0 win at Cologne in the Bundesliga on Saturday. Mallen got the opener in the 12th minute, finishing off a corner from Julian Brandt. Dortmund could have increased their lead still in the first half, but the second goal came only after the break when Niclas Füllkrug hit the net from the spot in the 58th. Mallen then completed his brace in the 61st after he received a stunning and long cross-field pass from winter signing Ian Maatsen, and Youssoufa Moukoko added Dortmund’s fourth in stoppage time. Dortmund remained fifth in the table…