"We're very proud," he told UEFA.com. "We played a great game and, although we didn't score all our chances, we managed to score a second goal.
"That's what matters because during the game we heard that Napoli were winning 1-0, so we gave all we had on the pitch to get over the line. We could have ended up first or third in the group, but we did our job well and took first place.
"It was important to finish top because Dortmund were finalists in this competition last year. This year it was a tough group; it was a tough group last year as well, but maybe there were people who doubted that we could finish top or even second this time. Perhaps we pulled off the impossible."
The winning goal came three minutes from time from Kevin Grosskreutz.