The France striker came off the bench in the first leg of the Champions League last-16 tie, missing a decent chance to make it 2-2 before Bayern ran out 3-1 winners.
That result leaves Arsenal needing to score at least three times at the Allianz Arena, and Giroud is not about to abandon hope.
"We need to score an early goal," he said. "In football you never know. We need to believe and stay focused, but we need to correct our bad defensive behaviour as well.
"I like to play against German teams because they are attacking all the time. There I get myself more possibilities to score. It will be an interesting game, for sure."
Arsenal are in danger of missing out on Europe's elite competition next season for the first time since 1997 and go into their final 10 Premier League games five points off fourth place.
Giroud said: "Of course we still want make it into the Champions League spots. We are confident, even though we recently lost the derby against Tottenham."