Hi Manish,
Regarding Forum bugs and feature requests: these are not Wix Code questions so this forum won’t get you the best answers that you’re looking for. please open a ticket to Wix Support .
Regarding freeze header in mobile view:
You can set an element as pinned to screen (up) in the editor, and use code to show it only on mobile pages.
See these:
HiddenCollapsedElement - Velo API Reference - Wix.com - how to hide/show elements
https://www.wix.com/code/reference/wix-window.html#formFactor - detect mobile
Hope this helps,
Liran.