French frontman Ribery said: "We didn't think it would be so easy.
"We know Arsenal are having some problems in the league, maybe they are lacking in confidence.
"But we feel good and we're delighted to have got that result.
"We're all working hard together, with the will to play well, to win, to defend together. It's important to carry on like this.
"We will have to match that performance in the return leg. We're in good shape to reach the quarter-finals but nothing is ever over in football."