Menu desktop and mobile (displaying problems)

Hello! I’ve bought your theme Sidney and I’m very satisfied with my result but I have a little problem. I’d like to see on the homepage a white banner with logo and menu like when I scroll the homepage (2), instead of when the site appears the header menu is transparent (1) and logo with the menu isn’t clear as I would like (white background). Can you help me please to solve this little problem? I hope so.
Please write me step by step what I must do.
Then on burger mobile menu is invisible, why? I’ve tried to apply all that you suggested in the other posts but nothing happens…I’m desperate because the site is already online!
www.elisarisitano.it
Thank you in advance! It’s very urgent!

NB I’ve already wrote 18 days ago…you’ve not answered…

2|690x388

Hi there,

We apologize for the inconvenient.

To change the background color of the top menu, use this CSS code below:

.site-header {
    background-color: rgba(255,255,255,0.9);
}

And to change the burger mobile menu color, use this:

.btn-menu {
    color: #455066;
}

Add both codes in above to Customize > additional CSS

Regards,
Awan