Changing Sidebar Width and Color of Hueman

I am trying to edit my sidebars in my WordPress Hueman theme. I want to interchange the width of primary and secondary sidebar, i.e I want primary on the left to be narrow and secondary on the right to be wider. Also I want to increase the width of the main content area little bit. I tried from different forums but somehow I am not able to do, there is always a big grey box left in between the sidebars and the content area. I want to get rid of that grey part as well and also change the background color grey of my sidebars to white with a thick black separator in between the sidebars and content area. I know this is too much I am asking but since I am totally new to WordPress, it would be very helpful if any one can give me single css code or the easiest way to edit my sidebars and content width and colors since I am not a technical person. Thank you so very much in advance.
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