0136 GMT March 30, 2020
City heads to Old Trafford for the first leg of the last-four encounter on Tuesday, having won the competition for the past two seasons, AFP reported.
Guardiola's side is third in the Premier League, 13 points ahead of fifth-placed United, but lost 2-1 to its rival last month as Solskjaer's men produced an exhilarating display of counterattacking football at the Etihad Stadium.
Asked what he had learned from that defeat, the Spaniard added, "How fast they are. How they run on the counterattack. How solid, how aggressive.
"We conceded a few counterattacks and in just two or three seconds they were in the box."
Speaking about Solskjaer, he said, "I think he is starting to see his team like he wants. The last (league) game against Arsenal they lost, but you see clearly what he wants.
"It was not easy to handle a team at a big, big club, always demanding to be champions in all competitions, but I think every manager needs time.
"I have the feeling United have started to play the way he wants."
With the Premier League title apparently heading to Anfield, Guardiola is forced to focus on the cup competitions after winning a domestic treble last year.
"A third semifinal in a row. It is not the best competition in the world but it is nice to be here again and against our city opponents," said the City boss.
Guardiola will have Nicolas Otamendi available again after an injury but has not yet settled on a starting XI.
"I have an idea," he said.
"We have played an incredible amount of games and some players need to rest. I have an idea, but I am not 100 percent sure who will play tomorrow."