V-belts

Hi boys,
I'll ask you a question about the belt. I guess it's due now, because I have whistling noises and when I look at the belt, it's also quite different to me. has a metallic shiny back side (which you can see when you look inside from above) and an abrasion track in the longitudinal direction in the middle. Is it possible that there is such a revolving roll or any aggregate leaving such traces? Is it enough to change only the belt? would be grateful for quick tips or help, as I don't have an appointment in the workshop yet and I don't know how urgent this is.
Greetings marchus