I see a lot of basic problems just from your op.gg profile.
Vision: You bought 1 ward in your last 20 games, no pink wards, never upgrade trinket. You use your trinket on average about once every 10 minutes. This absolutely needs to improve. You should be upgrading that trinket a lot more and using it constantly, buying extra wards, and buying pink wards.
CS: Low. This can be because you need to concentrate more on last hitting, but it can also be a symptom of simply getting annihilated in lane.
Deaths: High. This can also be a symptom of getting annihilated in lane and then not having any way to survive later, but you can always learn to play more conservatively from behind so that losing lane doesn't automatically mean you feed all game.
Items: REALLY needs work. You seem to go completely without boots in about a third of your games, and your upgrade is almost always Boots of Swiftness. You should always have boots before or around the time you complete your first item, and you should look to upgrade it before finishing your second item. Ninja Tabi or Merc Treads are much better than Swiftness for you. You build a Titanic Hydra or Ravenous Hydra in every game as top Olaf, and that's not a good idea. Grab a Black Cleaver instead and you will see your ability to fight your opponent go way up. You do not need a Hydra to clear out minions. Get tanky items after Black Cleaver, like Randuin's, Sterak's Gage, Dead Man's Plate, Frozen Heart. Never Bloodthirster.
I see more wins in your recent games than you used to have, which means that you are getting closer to your appropriate MMR. You'll start experiencing some games where you don't get completely stomped from start to finish. Feel free to keep playing ranked if you want to learn by playing hard fights, but understand that you do need to learn more about the game if you want to be able to compete. Watch some streams, watch some Olaf videos, and consider recording your games so that you can review them or have others review them. Also consider going into custom 1v0 games to practice last hitting in a controlled environment so you'll do it better under pressure.