Header effect (only when scrolling down)

Now: see f.e. that page and its curtain effect footer: https://enfold.webers-webdesign.de/

The content of that footer will end on small screens ( all columns are beneath each other ) at a height of 1176px.
So even if i could set that option when curtain effect footer goes to scroll to 100% ( only 90% option is available ) there will be no space to show all the content on f.e. an iPhone 11 ( screen-height is : 812px) – so if that footer stays on fixed position there will be 364px that could not be seen.
The only way to see the whole footer content is then to set position to relative and scroll with the content !

if we are talking about your homepage ( link on your nick) The footer is still fixed on my mobile devices.
but for mobile devices with less than 736px ( iPhone 6,7,8) it will scroll – because:
your footer height will be on that screenwidth of 375px : 535px and this is nearby 80% of available screen-height. That is the reason why i give you the snippet to enlarge the allowed footer height to set to 90%.
In this case your footer will be even fixed on Mobiles with 736px screen
if you got iPhone 5 it is 568px available – no chance even on 90% to have a fixed footer with curtain effect.

Yes on mobile devices – it is ok – but click on hamburger on desktop browsers! ( screens bigger than 768px)

this is what i see on all my browsers for screens bigger than 768px clicking the hamburger
no menu can be seen