The reigning European champions took a comfortable 3-1 win at the Etihad Stadium to move clear at the top of their group.
The manager told Sky Sports News: "We played good. We have controlled the game. I am happy for coming here in England against this big, big club and big, big players and playing like this.
"Naturally, we are so, so happy for our victory because we have six points at this moment, it's a good step.
"I think we played good. The pitch was unbelievable. When you have this pitch, this atmosphere, it's amazing. We are so, so happy to continue the job from last season and keep going."
Guardiola, who twice led Barcelona to Champions League victory, took charge of the German champions during the summer.