Flick's side, undefeated in 24 games across all competitions, are not taking Dortmund for granted despite carrying a 4-0 advantage into the return at Signal Iduna Park.
"I have a lot of faith in this team. We have gone through a lot of games without losing and we should be proud of that. I can't complain about a single one of my players. This team is incredible," Flick told reporters on Monday.
"The team should enjoy what they're doing, and we are ready to do it. We want to play well for ourselves and also for the travelling fans who always support us. We won't let our concentration drop."
While still chasing a treble as LaLiga leaders and Copa del Rey finalists, where they play Real Madrid on April 26th, Flick insists their sole focus is on the Dortmund match.
"We are only thinking about our game with Dortmund. The rest is for the future. We aren't looking any further. Our idea of football is about always doing our very best," he said.
"There is a lot of quality in our team and we always take things one game at a time. Playing Dortmund in the Champions League quarter-finals at their stadium is always going to be difficult."