The German struck in victory at Liverpool on Sunday.
"It was very important. I'm very happy to score my first goal here [Anfield] at Liverpool with their amazing fans and stadium," he said. "I'm also very happy that we won and got the three points, he told arsenal.com.
"You must always work hard in matches. You must fight, you must run and you must score goals. When I'm on the pitch I can win matches. Today was good, we won and got three points."