I'd suggest ripping apart the bike and putting it back together but not investing much (if anything) in parts just to see how things go together. Then go buy a better quality bike and go at it. There are deals out there if you look. Last month, I bought an '80s Centurion road bike that needed very little work and only a few $ in parts for $25 and the month before a mid-'90s Diamond Back MTB for $20 that just needed routine maintenance.