City’s qualification was sealed with a game to spare after a 1-1 draw with Borussia Monchengladbach in Germany.
Barcelona’s win over Celtic means the Catalan side top the group, with City guaranteed second place.
It leaves the Blues in the enviable position of being able to concentrate on their Premier League campaign, something Guardiola feels is vitally important.
“I’m so happy to be there (in the knock-out phase),” he said. “The first part of the season is so important, to qualify for the next round. We did it – and now we can focus on the Premier League.
“I am so satisfied for all the games. I was a trainer here in Germany and know how difficult Gladbach are. But we did it, which is why it is big congratulations to the team.”
City went behind when Brazilian Raffael netted with a fine finish from the edge of the area midway through the first half – but David Silva’s equaliser just before the break proved crucial.
CELEBRATION TIME: The City players salute David Silva after his goal
Guardiola said that was the key moment in the game.
“Yes, of course it’s better to go to half-time at 1-1. It was much better than losing and it was so, so important at that moment.”
City weren’t at their best for long periods, particularly in the first period where their passing was often too slow to trouble Gladbach.
Guardiola said it wasn’t a tactical reason, but wouldn’t reveal what he felt was preventing his team from reaching their full potential.
“At some moments, it’s not about the tactics,” he said. “The tactics are important, of course, but the reason why in the first half in some moments we didn’t play good is for another reason. The players know that and we are going to improve on that.”
Striker Sergio Aguero was seen limping towards the end of the game – but Guardiola allayed fears he had suffered a serious problem.
“Yeah, maybe he had a kick – but he is okay.”
