Real will go to Istanbul defending a 3-0 first-leg lead.
"The result is very good," he said, "but in football I have seen so many incredible things and nothing can surprise me. Istanbul is a difficult place to play.
"They have players with a lot of experience, great character and personality and they will fight very hard against us. We know we have to go there very seriously as that is the only way to get through.
"I think we played seriously in the first leg. The Spanish press are not so respectful to Galatasaray but we are respectful of them."