firstly, I would try to figure out whether this is network related or hardware related.
ie, is your hardware enough to run the game at stable 60 fps?
if yes, and you believe it's network related
You'll have to run some tests, basically check your ping to the game server and tracert the route. It's possible that you're going through different routers, where your router is overloaded by other people, while your friend has the router usage all to himself.
if you see any timeouts on a trace log you might want to try flushing your DNS.
Also, is your friend and you both on the same ISP?