Goals in either half from Pierre-Emerick Aubameyang and Nuri Sahin saw Dortmund to a 2-0 success on Saturday.
Since they lost the DFL-Supercup to Bayern Munich on penalties, Bosz's men have claimed three wins in competitive matches without conceding.
While the Dutchman was happy with another win, he wants more from his team, particularly in possession.
"I am satisfied with the result, but we still have to work on our game," Bosz said.
"Especially with our own ball possession. We have to move the ball faster against such a compact opponent.
"Nuri was very often free, but it took too long for the ball to get to him. If we got the ball to Nuri in midfield, then it became dangerous."
The win lifted Dortmund top of the Bundesliga on six points, having scored five league goals without conceding.
But Bosz said he had no interest in the league table at such an early stage of the campaign.
"The table is currently not relevant for us. I hope we can say that after 34 games, then it is important, but not after two games," he said.
"Nevertheless, we have scored five goals and have not yet conceded. That's strong."