Hi @paladinodeimari - are you looking at the right stylesheet? Because your CSS should only be showing the h1 and not the other elements (.menu-principale... etc.). So I think that's probably pulling in from somewhere else. Is your stylesheet named clc.css?
First, you can make sure it's outputting the font size and unit by going to your stylesheet in the HubSpot Design Manager and clicking on "Show Output", you'll see something like this:
Then, I would "View Source" on your page and make sure your stylesheet is being used. In the case of my "theme-overrides.css" as you can see in the tab above, it's appearing on my website as: