Trying to fix header logo so it doesn't jump about on mobile..

Hi guys,

I am having trouble keeping my logo from jumping about at the top of my website when scrolling on iphone. I am totally aware that it'll move as the bottom address bar appears and disappears on iphones, but this is more jumpy and distracting than on other sites I have seen.

I have added a fair bit of code to the site but if anyone can help it'd be much appreciated! 

Website: studio-teller.co

Issue is on iPhone 13, have not tried it on android.