Berrarda left City for United last summer and oversaw the dismissal of Erik ten Hag and the hiring of Amorim as his replacement.
"It was difficult in Pep's first year," said Berrada.
"He didn't win anything and there was suspicion about whether he could implement his football vision in the Premier League. People said he was arrogant and wouldn't change his style of play. But he stuck to his principles."
Asked if he saw similarities with Amorim, Berrada said: "Very much so."
On next season, Berrada was optimistic.
He added: "There'll be some difficult moments ahead.
"Nothing is going to get solved with one summer window, but we are on the right path.
"We've put the worst part of this transformation phase behind us and now we're going to start building. I'm very confident we'll get back to the top."