Ok, I got the problem with the CSS.
I modified the CSS I use for the template (like typography.css and style.css).
But I've just noticed in the hikashop's options I can choose which CSS file use for customize it. Both of them in the Media folder.
I don't get why first hikashop use the proprieties of my css file (and for me would be obviously good), then when I click on the chart icon and I get misteriously logged out, and I do the login again, then hikashop uses its right css file (default or custom one).
And also the mistery of the first page after the login. Sometimes the Edit account page (even if I disabled the option for the User account link...right now I have it activated anyway..), sometimes the page with the icons that link you to the Listing orders page and the Edit adresses page (and that is the way it should be).
Gonna check the following days...then gonna give you my feedback.