I've watched many video guides on peeking, counter strafing and crosshair placement, and I still can't improve

I play 1 to 2 hours a day

I play DMs (no comp cuz I don't have a mic yet)

In long range duels I try to shoot, they wiggle left and right and I can't shoot them, meanwhile they get me with ease

When I press A/D to strafe left and right so they can't hit me as easily, boom getting one tapped regardless

When they A/D strafe they are somehow able to hit me while my shots while A/D strafing go everywhere

How?

When it comes to peeking, idk exactly how to peek, I'm aiming at a corner, then all of a sudden a player slides sideways out of the corner and one taps me in less than half a second, how am I supposed to react to that?

I even try to crouch as I approach a corner, yet they still get me

And lastly, even if I do have my crosshair at head height, I peek out of a wall/corner and also counterstrafe to stop my self and shoot accurately, they still get me first, how? Is their reflexes/reactions just faster? If yes, how do i improve my reaction time?