Top-lane fighter.. advices?

Hi all! I am a newbie player, maining mid and utility support. I love the mage playstyle, staying far away throwing stuff in xD Trying to play even other roles I found out I may like adc, for it being a role that stays at the border of the fight too. But, I have some abnourmous troubles with the champions that must go inside the enemies... which makes top-lane a nightmare for me. Now, on tanks even if I am bad and dislike the role I at least have an IDEA of what I should do... On fighters though once the lane is over I have no clue what to do.

For example I just had a game with Fiora. Even if I in general dislike melee champions I enjoyed her a lot: nice mobility, and the mechanic of dancing around your opponent for maximum damage is just wonderful imo. I really had fun :D I took 3 kills in lane, then I tped mid during a fight and took a triple. And, the enemy team started grouping around. And I sarted dying literally every fight ( I finished the game with 11 or 12 deaths :O ), even if I parried nice I couldn't parry everything! I built tanky , so I wasn't able to one-shot corki or Ahri after some points ( and they had a Janna.. ;C). I didn't know what to do: If I jumped on corki and kept chasing him, with Janna around, I had a double after discovering my whole team had died bc Cait was getting oneshotted by Ahri or Volibear. If I turned around to help Cait trying to slow down the bear we would die all..

If I splitted they would have free objectives as 5..

So.... what are you supposed to do in the game as a fighter?