dont play either fiora or irelia when youre still learning the game.
if you want to improve at league of legends, play garen, mundo, nasus or similar champions until you have the games fundamentals down. (no, if youre bronze then you really havent learned enough of the basics)
the advantage of playing these champions is that youre not fiddling around and investing 50% of your concentration while youre playing into how to even control your champion, but that you can focus on csing, map awareness (do you know typical enemy jungle pathes and camp clear times to anticipate ganks?), lane control (do you know how to really freeze a lane? when you should push and when to recall?), damage checks, tracking enemy (summoner spell) cooldowns, overall macro play and similar mechanics of the game itself.
if you can get to plat only playing garen, nasus or mundo then you probably have understood the basics of the game well enough. on your way up, you can decide if you want to branch out into new champions and increase your champion pool.
here again. dont pick the most complicated and flashy champions you can find. look at
and others.
if you make it to around plat with these champions you can start thinking about picking up more mechanical difficult champions and learning those, and focus on more mechanical outplays.
this is a mistake a lot of players make at your mmr. you pick complicated flashy champions like zed, fiora, irelia and yasuo that are difficult to just pick up and learn to play and you only end up focusing on how to manage the champion and dont learn how to actually play the game, and end up feeding most of your games, then coming here and complain about people beating you with mechanical simpler champions.
the general rule is, if a garen beats you in top lane, he is just probably better at laning and laning mechanics than you. because the champion itself doesnt outright beat many matchups.
by the way, there is always more to learn. we have garen mains at master tier and sometimes even upwards into challenger just because these people have mastered macro play and matchups with the champion. this proves that you can always get better at the champion and the game, even with a champion like garen who is relatively simple on the surface.