First of all, I like your icon, is that available in the shop?
And as far as Swain, playing anyone ranged top introduces another factor of skill which is kiting. Fiora has a lot of tools to make you work your butt off to kite her out and she's easily going to parry your claw every single time.
The best way to beat her is to totally avoid letting her get damage on you early, if she gets a cc on you, you're going to lose every trade so you should really just cs from range until you have some hp or seekers. When you do feel like you can all in her (definitely wait for 6), try to let her wave stack a bit to maximize your aoe healing and stand tight to a wall to stop her from getting one of her ult marks. The first time you do this right, you'll probably laugh as it can completely nullify most of her ults value.
I feel that Swain top is actually really underrated and taking grasp of the undying can really pay off, especially in a lane like this. Grasp let's you stack significantly more hp in addition to your passive and then you have a reason to take boneplate which will seriously reduce the damage from her trades.
Also, don't ever ignore the value of ninja tabis. Tabis are honestly just straight op into any AD auto attacker and that reduced damage will mean a lot more in a 1v1 than the damage from sorc boots.
In summary, this is a scaling lane and absolutely has to be played like one.