Bayern host the second-leg defending a 3-1 lead.
"This is a completely new match. We are only at half-time in this tie, and we must go there with belief," Gervinho said.
"We have to believe in ourselves and our talents.
"I know it will be difficult, but I still believe in us. We are going through a tough period at the moment, but there is still a really good spirit with this group of players.
"Just because we lost the first match at Emirates Stadium, we will not give up."