Remove Sidebar on specific pages

Hi there all

I am going nuts cause I’ve googled all night and tried all sorts of things but nothing worked

First of all this is my blog : https://www.sumo.gr

I am using the Twenty Ten theme

What I want to do is remove the sidebar on specific pages like the “about us” page and some more

If I select “one column – no sidebar” in the page option everything shifts to the right. Even if I widen the page to 900px in the style.css file nothing happens

Note that I have changed the default sidebar column from right to left via some code I found googling

Can anyone please help?