iPhone 4 cannot update or restore through iTunes

Dear all,
I have a iPhone 4 16 GB, bought in September of last year.
I havent updated the phone in a while, and since a couple of months I am trying, and after downloading the update through iTunes, i get the message: Cannot reach the server.
The same happens when i try to restore the iphone through itunes.
The iphone is entirely original so no jailbreak or unlocking.
I am not a pro, so if someone could help me in dummy language, i would owe you my life haha
version: 4.0.2
modem firmware: 01.59.00
iphone 4 Other OS