Speaking to Manchester City's official website, the central midfielder said:
'I’m thrilled to have signed for Manchester City.When I learned of City's interest my heart was set on coming here and things have moved very quickly.
'I have loved my time with Borussia Dortmund and I would like to thank the club and the supporters for the five very happy years I spent there. They gave me a platform to play on and I became a better player because of the belief, patience and trust they showed in me.Now I have a new challenge and that is to achieve great things with City. The opportunity to work with a coach like Pep Guardiola is something I am really looking forward to and I am flattered to be the first signing the club has made this summer.
'I can promise the City fans I will give everything to help us win titles both in England and the Champions League. These are exciting times.
I have my best years ahead of me and I think we can achieve great things together. I can’t wait to begin this new chapter in my career.'He also shared this on facebook: