The 25-year-old has failed to make an impact at Betis after three seasons at the club.
“I am going to leave Betis and I would like to return to the Bundesliga,” he told Express.
“I think FC Cologne would be a great club to join, their general manager Michael Meier knows me well from my Dortmund years.
“I would also like to play alongside Lukas Podolski, that would be fine. And it had been at Cologne where I scored first for Germany.
“Joining Cologne would be a great thing.”