Hello. When I'm riding downhill on my mountain bike with 21 speeds, the pedals move forwards, and when I pedal backwards the chain doesn't move smoothly at all through the rear derailleur and often gets stuck. If I just keep my feet still the same thing happens as when I pedal backwards. It is a brand new bike right out of the box and as soon as I rode it for the first time, It was messed up.
Thanks for the help, It means a lot!