Iphone5 stack in itunes screen and cannot restore to factory defaults due to error

Dear community,

I have recently bought an Iphone5 from a close friend in perfect condition. Unfortunately after a few days of good operation it started switching off (going completely blank) so i had to reset a few times. Another 1-2 weeks passed with a few incidents when in the end the screen stack on Itunes and i cannot even restore to factory defaults through the itunes program (i always get an error 14 and i have tried different cables/usb ports/laptops etc).

I would appreciate any help to bring it back to life.

Regards,

Kostas