Gundogan then added a second on 53 minutes to give Man City a resounding 4-0 lead in the tie, with the second leg at the Etihad Stadium coming up in three weeks' time.
"An excellent result. We are almost in the quarter-finals," Guardiola told BT Sport. "Champions League is always 180 minutes and we will take the game seriously but it's an excellent result.
"Ilkay Gundogan is an extraordinary player. Last season we missed him a lot with an injury for six months and that's why we are so satisfied, not just the quality but personality to play.
"We are still in February and in the Premier League we are in an amazing position and we are almost in the quarter-finals, we are in one final and on Monday we have the opportunity to reach the quarter-finals of the FA Cup. Game by game."
Man City travel to League One side Wigan Athletic in the FA Cup fifth round before a trip to Wembley Stadium on February 25 to play Arsenal in the EFL Cup final.