My bike is too big for me
 

Hi, i am 5'8" and recently my uncle gave me his bike ('09 haro shift r1), which is a size large. I love the bike, and i really want to ride it comfortably, is there anything i can do to make that bike fits me??

My guess, lower the seat post and move the seat forward.

Are you able to purchase a shorter stem for the handlebars? If you can that might help quite a bit.

oh ok, shorter stem, and i will move it forward?? when i rode it hurts my lower back, nowhere else but my lower back, well it was the 2nd time i rode that day...

Trade it for one that's the right size. I acquired a mountain bike that's too small. Nothing I've tried will ever make it work right for me. It's going on Craigslist.

that's a good idea