Signed in a club-record deal from Benfica, the 21-year-old said he wanted to progress as a player while helping the team to achieve results on the pitch.
“I am very proud to join this club, a great English club. In history, they have won two European Cups and I am very happy to be here,” he said.
“I want to help the club to get good results and hopefully get back to the Premier League.
“The fact that Aitor Karanka is the coach played a big part. His teams play good football and that is very important for me. I hope that with him, I can progress as a player and hopefully I can play well for him.
“In the beginning, I will need time to adapt to English football.
“But I think that will happen during pre-season. I will be ready and adapted to football here to start at the top of my game.
“The responsibilities are the same. Benfica is a big team and the focus is to win and win titles. Here, it is a different level but Forest is a top team as well so the responsibilities are the same; to win week after week in order to finish the season with promotion to the Premier League.”