Won"t go forword but will go backwords

I have a 2008 bad boy buggy ,MTV.The charging gauge says its is fully charged. But when I attempt to go forward ,I can only depress the accelerator pedal to start it will start moving slowly but as I start any kind of incline or attempt to speed up it stops. I then have to turn the key off and turn it back on only to have the go slow or it stops again. Any ideas ? thanks !