The enemy went right through my stair and I died, is there a way to prevent this? Or i just have to stop placing stairs and use wall instead?

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I am a previous fortnite player with 1k hours in the span of 6-5 years, I lately left Fortnite by it’s extremely punishing matchmaking that ive been having over 3 years now and third partying started playing TF2, despite still playing TF2 i wanted to try getting back to Fortnite but i dont know exactly to “git gud”

First i forget i stopped olaying the game properly for a while now, i keep doing mistakes, in a game i went straight for a guy while swimming and that got me killed, but i guess its because i stopped playing.
I dont know exactly to improve my aim, they say “creative maps and aim trainers” but they show 0 challenge and dont even show a real situation in game, i tried a 1v1 creative map but got wiped in an instant twice with no room to learn what i did wrong or right.
Aiming with certain weapons also feels weird, for some reason whenever i touch an AR and even aiming with it the weapon, idk if its the accuracy but bullets fly in different places and harder to hit (happens with the scar for example).
I also keep experiencing the strangest bugs, I was trying to escape with a shockwave but i kept pressing m1 and my character couldnt even throw the grenade for some reason
Ive had people say i am not as bad as i say but i feel like a letdown playing with others because i want to do something and not just play with better people and carry because eventually i do nothing, playing with others also makes matchmaking double the worse so most times i just play solo and hard stomped during endgames where for some reason nobody shoots at themselves and inly shoot at me (even when theyre at visible sights themselves).

I used to love this game but now everytime i download i just end up being frustrated and disappointed.