So I could usually download a demo of 856 mb in like five minutes and my games were lagging and stuff, so i formatted my hard disk and now for the 856 mb download it says its gonna take three hours...
Power cycle your modem and router. Unplug your modem and router > Wait a minute and then plug your modem back in > Wait for the router lights to normalize > Plug your modem in and wait until the lights also normalize.
Also try changing your DNS servers to:
how do you change the server?
Sign into your router configuration page and look for the DNS entries. You'll have to consult your router's documentation or Google your router model number to figure out how to get there.