The second leg will take place in London after a 1-1 draw in the first leg.
"We know that we are a difficult team to play against at the moment, but at the same time we have so much quality up front and in the way we play," Christensen said.
"So there's no extra pressure from our side, we will just try to do what we normally do, what we've done for so long now, and at the same time show our quality going forward.
"We changed the system, which obviously worked really well, and every game we are growing, not just as a back five but as a whole team. We're trying to be a very difficult team to play against, a horrible team, and then as soon as we get the ball we want to play good football, quick football, with a lot of energy.
"Everyone's just trying to work on the same idea, there are new ideas coming across that we've tried to take onboard very quickly, and at the moment we're growing and when things work out you gain confidence and you're just trying to do the same things, work on the same things and make things work even better than they are at the moment.
"There's a lot of structure and a lot of discipline involved, especially when we don't have the ball. We want to bring a lot of energy, we can't let them breathe too much. We try to be smart about it so we don't run ourselves out of energy at the top level. As soon as we get the ball we either take it calm or we take a quick decision to play direct.
"Against teams that are used to having the ball a lot, we might need to herd them, if that makes sense, and when we have the ball they might not like to run, so we need to use that. So we are always thinking about what we can do to help ourselves and there's a lot of details to it."