Fortnite Good Aim?

Hello if I make an aim course for half an hour and then play games my goal is good for a short time and then I meet again why is that why it does not stay that way I have a good aim to build the qber is never so edit eig works well too.

I think you lose your concentration after time. Try to concentrate better.

Should I focus only on my aim first.

Yes, try to focus as much as possible on your Aim until you have subliminally good Aim. Otherwise, make sure you stay calm in stressful situations.