how doI repair the back window wont go up or donw motor is workig

Take the door apart and see what the problem is. Most likely the "window regulator" will have to be replaced.

if you are replacing a regulator, I find the window regulator/motor assemblys from auto zone work the best, and entire bolt in assembly.

The motor will work most of the time, BUT, they have a little strip of plastic that goes through a deal that raises and lowers the window. They brake. Buick is bad about that. I had to go to the junk yard and get one for each side on my 01 Buick.

the cable on the window regulator is broke or the teeth on the gear are stripped. need to take the window regulator out of the car.