Patrick Dorgu struck the winner in the first-half, with Amorim admitting United battled to secure the three points on the evening.
He said, "We need to suffer all together in the stadium. In the game really difficult for us. I think we did a good first half, and then the second half, we just defended, tried to do something with (Matheus) Cunha. We had the opportunities in the second half with transitions, but it was a good win. But I had so many games here saying we played very well and didn't get the three points, today was the opposite. I think we suffered together and we managed to win the game.
"I think we spent a lot of time with each other. We had some low moments and that sometimes can bring good things to the group, but it's good to have that feeling to have the experienced players helping the kids in helping the team understanding we are suffering. It doesn't matter if you're outside the pitch, you can play the game, and I think everyone played the game."
On changing the formation, Amorim explained: "In the first half, I think we showed that I felt that was the only way to create more danger, to have more opportunities was with the back four with a lot of guys inside. Even to keep the ball, because I remember the game last year we lost one against one outside. We just tried to imagine the game and to help the players to feel comfortable."
The manager also said: "It was the opposite of many games at home when we played better and created more chances and didn't get three points. We did a good first half and then in the second half we suffered with the fans.
"They are a very good team and I think we put some players in positions they are not used to. We put players in who don't have a lot of experience at this level. The context of the game was hard for us but we won and tomorrow people just remember the result.