macbook air

i just installed a new mac os and it was working great for the past week then this appeared and i know how to re install mac os but i would like to have windows as i could download so many more things but is there any way to download windows on a usb without having to install mac os on this again. my buddy has a computer i could borrow for it i just really need something to do my work on and i’m honestly tired of mac os thanks!