I think you need to just realize that top lane is usually for better players. No offense, but unlike other lanes, Top is 1) the only lane that has pure hard counters by 5-6 COMMON picks to every other top laner and 2) is the primary jungle ganker lane.
For example, a Riven has at least 4 natural enemies top, but that's effectively her only meta role. If it's not a GOOD Riven, Garen, Wu kong, Panth, and Darius all make Riven's life a living hell. Riven has almost no counterplay against dying to a Garen, and if Pantheon gets 1 kill, Riven is shut down for the entire lane.
Likewise, Garen has natural enemies.
And i don't mean just hard matches. I mean these are matchups where 9 of 10 games you will lose so hard your team has no choice but to carry you.
Top is basically the only lane where the majority of times, the matchup is decided in Queue, by who gets to pick Top second and who knows counters.
Adc, mid, support, and even jungle don't suffer these problems near as much, because Adcs can outplay relatively, and have supports to supplement their weaknesses, and Jungle is given the opportunity to avoid the other jungler and work around them. Mid champs are more balanced, and usually have pretty reliable turrets to help them if they should have problems.
GP is a lane bully and has been for years. That's nothing new. You need to learn to rely on your team to beat him. If you can't get your team to help, or play a ranged champ, my advice is to leave the lane, farm some jung, and go help other lanes. if you leave, so will GP, and then your team will begin to pay attention to him. If GP doesn't leave, and keeps pushing, your team will still pay attention to him because they don't want to lose their base.
Personally, as a jungler, I enjoy bullying GP, because he's an easy gank. Just have to avoid the barrels, and get him from the right angle to make him run the right ways, and have a peel to escape if he gets dangerous hits in. Usually, his ult will be down, so escape usually isn't hard.