City moved into the Champions League quarter-finals for a sixth successive season with an 8-1 aggregate win over the Bundesliga side.
Haaland’s five goals meant he has now scored 39 goals in all competitions this season - breaking Tommy Johnson’s Club record of 38 in a single campaign set in 1928/29.
“Five goals, what can I say?” Guardiola said. “I said many times, he’s a joyful guy. His mood in the locker room is always happiness.
“He is a gift to all of us. He is a huge competitor, his mentality is there. He scored five goals which is not easy.”
Haaland has five hat-tricks already this season and his 39 goals have come from just 36 matches.
But as well as his goals, Guardiola praised the striker for his all-round performance and says he was more involved than in recent games.
“Today he scored five goals and I think he made 30-35 ball contacts and this is what we are looking for,” the boss added.
“I had the feeling when you are involved in the game offensively, defensively, when the ball comes to score a goal, you are more clever, more precise, you are in the game.
“It’s difficult to score - he can do it though - when you don’t touch the ball for 40 or 50 minutes.
“Sometimes it’s his fault, sometimes he doesn’t move. I said in Palace, you didn’t play well today. But other days, it’s our fault.
“In Leipzig, we could not find him. We did not find him in the second half. Sooner or later we are talking about, we are working a little bit and everyone because we try to make the process sometimes quicker.
“I would say we have to be slower. But once we break the holding midfielder, we have to be quicker. Sometimes the people think that defensive line-up, we are going to play slowly, we are going to play comfortable but our mentality has always been so, so aggressive from the day one and sometimes we cannot do it because the opponents are there.”
Haaland set more records as he became the youngest player to reach 30 goals in the Champions League, doing so in fewer matches than any other player in the competition’s history.
He also equalled the record for most goals in a Champions League game, matching Lionel Messi, for Barcelona, in 2012 and Luiz Adriano, for Shahktar Donetsk, two years later.
With the tie essentially killed off after his fifth made it 6-0, the boss substituted him in the 63rd minute with Burnley in the FA Cup coming up on Saturday.
“If he achieves this milestone at 22, his life will be boring!” Guardiola said. “Now he has a target to do it in the future, that’s why I made the substitution.
“I didn’t know it happened with Messi, they told me. I made a substitution because normally when a game is over and I want use as many players as possible.”
