I was able to solve it, thanks for responding so quickly. While setting up I noticed something.
The banner that I placed on the site is not a static image placed by Customize>Frontpage Options>Banner Advertisement>Show banner advertisement, is a custom HTML code placed by Widgets> Front Banner Ad Section. For it to appear I had to put an image by Customize>Frontpage Options>Banner Advertisement>Show banner advertisement and in the additional CSS put display: none; in .banner-promotions-wrapper img. That is, the Widgets of the header depend if you have an image placed in the Banner Advertisement, is it anyway?
