The Spaniard says he is still adjusting the style of play in the Bundesliga and has warned his side that it will have to be on top form to beat Dortmund.
The former Barcelona boss took over from Jupp Heynckes at the Allianz Arena this summer following the Bavarians' treble win last term. Bayern is currently four points clear at the top of the Bundesliga but Guardiola feels he is yet to really exert his influence over the players.
"The team are a little better than before, but it's still not my team," the ex-Spain international said at a press conference. "I need more time. We have had very good results, but my game style is completely different. In Germany, there's a counterattacking culture that's not part of my game.
"It's a process: I can't say that we are great because we're top of the table and we have qualified in the Champions League. We're still not great."
Bayern has the chance to pull clear of nearest rival Borussia Dortmund when it clashes with Jurgen Klopp's side at the Signal Iduna Park on Saturday. Guardiola said that he was looking forward to the match, but warned his side of the threat BVB pose.
"We play and coach for games like this. We're really lucky that we have this opportunity. It's a big, big match," the 42-year-old coach said. "They're the best team in the world at transitions. If we let them run at us, we won't stand a chance. We have to play as well as we possibly can."
The European champions have a number of injury problems going into the clash but Guardiola is refusing to dwell on their fitness worries.
"It can't be an excuse - I hate excuses. It's a bit of a problem, but I'm mainly sad for the players."