Foden netted the only goal of the game in the 36th minute, latching onto a superb backheel from Raheem Sterling to fire into the bottom corner.
The 20-year-old was the star of the show for Pep Guardiola's side, constantly looking to breach the rigid Olympiakos rearguard and he expressed his delight at progressing into the next round, but wants the team to focus in the remaining two group matches.
"It feels really good to get the qualification done today, we're looking forward to the next stage, but first of all, we need to finish off strong," he said.
"I always love scoring for this club, I enjoy it a lot and I'm trying to score as many as possible. It was great vision from him [Raheem Sterling] to backheel it to me, so I'm thankful for the assist."
The midfielder also spoke about how he's feeling at the moment and touched on the gruelling upcoming schedule ahead of Christmas.
You can hear the entire interview by clicking on the video above.