1997 Other Volkswagen Models lost reverse gear

I have a 1997 volkswagen cabrio and I recently lost reverse. You can put it in reverse fine but when you try to back up (especially on snow) it pops out and grinds and chatters. I was told there is a adjustment for reverse but im not sure what to look for and where it is since we've never owned a volkswagen before. What can be done to fix this or will it require a whole new transmission?