Complex sentence: He made his debut on 10 August, starting in a 4--1 win at FC St. Pauli in the first round of the DFB-Pokal; five days later he made his league bow in a 4--0 loss at Borussia Dortmund.
Split into simpler sentences: He made his debut on 10 August, starting in a 4--1 win at FC St. Pauli in the first round of the DFB-POkal. Five days later, he made his league bow in a 4--0 loss at Borussia Dortmund.