The Norwegians ran United close, with the hosts eventually winning 3-2.
Amorim said, "I think we improved different things since the last game.
"Was special because half of the stadium doesn’t know me and you can say I came from Portugal and half of the stadium doesn’t know me.
"And I have done nothing for this club yet but the way they support me. In the beginning I felt that I am not alone here, I am one of them now and it was really special and I really hope I do not disappoint my supporters."
On two-goal Rasmus Hojlund, he said: "I think he improved the connection.
"I think he has to improve more because sometimes he gives too many touches when he holds the ball.
"But he’s really important for us because when we are in the low block he is the guy to hold the ball, to connect for transitions, he did that very well, he has that characteristic, he was aggressive in the goals, he was aggressive in the box and he is a quality player.
"I think he scores the most difficult goals so he has a lot to improve. Is the same for every player but he did a great job today."