how to fix door window

[slowboy]

To roll window down, it acts like it is on steps...crank half inch, stop and back handle up...crank another half inch or so, etc. until it finally reaches bottom. To roll window up...I have to take left hand and pull up on glass while cranking handle. I think maybe a screw came out of glass because when you pull up on glass, the glass can be 'rocked' back-and-forth, up-and-down. Anyone want to tell me the steps on how to fix this? Please ! !

Thanks ! !

Keith