iPhone 3gs boot error

My iPhone 3gs boots into DFU mode. I've tried all kinds of loop fixes but they don't work. I bought this iphone frome someone, the glass digitizer screen is cracked but i checked the logicboard and it seems fine is there a way to repair the booting process back to its original state. Also I've come to the conclusion that the boot process is the problem because when i try to restore i get to preparing iphone which it is where it should reboot but the screen just glows then i get error 21 if i restore to ios 5.1.1 but this iphone messed up on 4.3.3 so that and under i get error 3194.