How to delete the white bar above where the site title goes in Resolve?

Hi Roberto, thank you for your question!

The white line that appears in the header is a static style in the Resolve theme and unfortunately it cannot be changed with any of the available controls in the Customizer.  However, you can utilize the custom CSS option to target that element specifically and make the necessary design changes.

That line element in the header has some margins applied to it, and there are a couple solutions you could use to get rid of it.  The first option is to prevent the element from rendering on the page entirely and doing this will adjust the positioning of the elements on your page.  Here is a snippet that will hide the line altogether:

.header .line-lg {
    display: none;
}

The other method is to make the color of the line to transparent, which will still hide it, but preserve the currently spacing your have for your page content.

.header .line-lg {
    border-color: transparent;
}

I hope those snippets help you achieve the design you want and please let us know if there is anything else that we can do to assist you!