Hi there,
add this css code to your css/custom.css

.uk-nav-navbar ul a:hover {
color: #fff;
background: #387eb2;
}

I'd love to be so good to identify the classes to change. I'm trying with the Chrome web inspector (I don't know if it is its name in english), hoping it's a good instrument for this. For example I want to reduce spaces between elements (particularly in the sidebar) and I'm not been able wit the customizer (spaces section) and I tried with custom.css to implement the uk-panel class like you did above with the hr.style (it seems for me to be the class relative to the sidebar elements) but obviously it doesn't work. How would you do this?
Many many thanks for the help

Hi there,
which space do you mean?
Inner Space ( padding) or outer space ( margin)
Here is a video how to find the css classes and check the spaces.
www.joomlaplates.com/template-customizing

GOT THEM!