Yoshinori Muto is only thinking of a future with Mainz.
The Japan striker is being linked with a £12 million move to Manchester United.
But he told BILD: "I've had a lot of chances.
"Yes, I've scored a few goals. Nevertheless, I am not happy with my performance! I have to improve in every aspect."
Muto added: "It's just been very different. But because everyone helped me it's never been the point at which I thought I have done the wrong thing.
"The move to Mainz was absolutely right!"