Got this bike super cheap so I could ride while saving for a good bike. Adjusting on the rear derailleur, it is a reverse styled, and it will only shift through gears 4-7 cleanly. I try adjusting on the screws,cable tensioner etc but it goes from shifting through 4-7 fine, to shifting from 5 down to 0 (falling off the first gear and getting caught in the frame. Think this is just typical big box store junk or is it something able to be fixed? Thinking about just leaving it alone with 4-7 and scrapping it all when I get my new bike.