Oihan Sancet's penalty for the visitors was sandwiched by goals from Lamine Yamal and Robert Lewandowski for Barca.
Flick said: "I am more satisfied today than in Valencia. I am very happy for the victory. I am also happy that Pedri has returned. Sometimes, there has been a lack of calm, but it is good to have passion and intensity."
On Lewandowski, he continued: "I know him very well, I have worked with him. He is a very professional footballer. He works with great intensity. It is not a question of age with him either. If you are fit and positive, you make the difference. Knowing how to score and press. With one on one he continued to press.
"We needed the goal, and he had the opportunity. It is his job and he does it one hundred percent and it can be done. He always receives the ball very high, this is part of it. of our game. In the first half, he could have scored one or two more goals. That's my impression from the bench. In any case, he is a scorer.
On his start with Barca, Flick also said: "I am always positive in relation to the games and the competition. We must change what we cannot change. We must not regret what we have not done. The injured are progressing well, and I hope to have them recovered soon.
"Christensen also has some problems and we have to be careful, if he's not 100% he won't be able to help us. There's a good defence, and with Éric we're doing well like that."