Hi,
You may use the following code to your custom CSS:
#sp-header, #sp-header.menu-fixed-out {
top: 350px !important;
}
#sp-header.menu-fixed {
top: 0 !important;
}
This will let you down your menu a certain distance! So please use the top value the same as your video height within the first portion of the above code.
I am unable to reach your site, otherwise, I could measure the exact distance!
And while you scroll then your menu will go to the top position again.
Best Regards