Thursday night's first-leg finished 2-2 in France.
Amorim said afterwards: "I think it’s 50/50. And then we have to be really smart in the next round, because we are going to play at home and our stadium with our fans, and they will give us energy.
"But at the same time, this team of Lyon wants to push us to make possession near the box, to have a lot of space to make transitions. So the next stage we need to play of course, with our heart, but we have to think a lot during the game.
"So it's a really difficult match, but again, we are playing with our fans and when we play at home, we play with one more player.”
Meanwhile, Amorim praised the performance of goalscorer Leny Yoro.
“Yeah, it's really good. He's really confident. I think he's improving. The physicality was something that he was struggling.
"He didn't have pre-season so we had to maintain Leny sometimes with a little bit problems and we start again. So we are seeing all the work that all the staff is doing with Leny. He feels at home in Carrington, in our club. So you can see that he's a top, top player.”
On fellow goalscorer Josh Zirkzee, Amorim was equally pleased.
He added, “Sometimes the most important player in the game is the guys that come on during the game. So he did his job quite well. But again, Rasmus (Hojlund), especially during the first half, he did a lot of runs and pushed the team forward, in one moment that we were struggling to find the right moment to press the opponent. So he did his job. And then Josh did a great goal and also did a great job when he was inside of the pitch.”