background for header

I don’t see the image on either site… but anyway the code for the header

.head-container {
position: relative;
left: 0;
width: 100%;
display: block;
background-size: cover;
background-attachment: fixed;
background-position: center center;
z-index: 9;
}

I think in this case the ‘background-size: cover;’ is affecting the image if it is not big enough

If you don’t already have a child theme or a custom.css you should install a plugin like custom CSS plugin then add the following to the custom css area.

.head-container {
background-size: 100%;
}

or

.head-container {
background-size: contain;
}

thanks for the fast response
And how to make it same for different browsers? (now I made it for chrome) does it depend on size?
you can check it now