The only thing you have to do against GP is to kill his barrels. You won't kill them all, but his barrels are his everything.
Damage, waveclear, poke, escape, CC. If he lands every single barrel on you then yes, he's broken. If Ezreal had a way to land every Q on the enemy champion/s he's facing, he would be more broken that post-rework Skarner.
I recommend to play either :
- Champions who have AA-reset abilities (
etc etc). Hit the barrel as soon as it has 2 hp then quickly reset it, it even gives 10g!
- Ranged champions. Your extra ~400 range over what melees have is more than enough to be safe from his barrels, unless he chains all three (and then you have like 20 secs free of harass).
And to watch this video. I watched it yesterday, so I mostly summed it up and added my personal thoughts, from a top lane main.
Also, if you want a definition of lane freezing. By pushing a little bit faster or a little bit slower (or not at all and last-hitting), you can change the place where ally and enemy minions meet. Use this to your advantage.