Any idea how to make a fixed header but keep a scrollable logo only? (Mobile and laptop)

Hi,

I'm trying to make the logo scroll only but keep the header fixed on my website. 
Would like to know if anyone could help me. 
link: https://www.yoistore.co.        

password: 987654321

Bests, 

Yoi

I think I sent code in another thread

Use this CSS (Design > Custom CSS)

a#site-title {
    position: fixed;
    left: 50%;
    transform: translatex(-50%);
    margin-top: -10px;
}