please help, how do i make the whole sites background just white?

Not sure what you are seeing as it looks white to me, but if you mean the area of the menu for the current page, the grey is set here:

#menu li.current-menu-item a {
    background: none repeat scroll 0 0 #DDDEDE;
    color: #3788C1;
}

oh thanks
click on the blog tab, youll see what i mean
there is gonna be a big black gap in the bottom of the menu items

Looks like you’ve made a lot of modifications to the theme? You have many mark-up (HTML) errors — so those are likely causing problems:

https://validator.w3.org/check?uri=http%3A%2F%2Fpaolorubini.com%2Fblog%2F&charset=%28detect+automatically%29&doctype=Inline&group=0

https://codex.www.ads-software.com/Validating_a_Website

You may need to validate the CSS code as well.

If the errors are in the theme, you’ll need to contact theme forest for help, as commercial themes are not supported here.

Ok thanks
I did not touch any of the portfolio HTML
i only touched the CSS a little bit
if you click on the Blog tab, it shows a black rectangular box on the bottom left, i dont know how to get rid of that
anyone can help me please?
this is urgent!!
thanks all!