Issues with responsivness

Hi,
I am having issues with the responsivness of my site :
1- The breakpoint doesn’t arrive soon enough so my nav bar is pushed down rather than being “compressed” in the hamburger menu :
https://imgur.com/a/YXsPnD5

2- When on a small window, if I do an horizontal scroll I discover the (blue) background and the page doesn’t come back in place automatically (as it usually does on Mac).
https://imgur.com/a/YXsPnD5
(And also : where do I change this blue color? My website’s background is set to White).

Thank you !

Ticket