How to reduce the size of the site template?

Question

css

codepen.io/kazzkiq/full/pvqvxO I created a similar site, but it turned out that the content on the site takes up very little space, and I want the size to decrease by a third, for example www.mvideo.ru/deal_of_the_day , only the main information about the product is shown , but everything is empty behind the product, only what is needed is also shown here, and the "second" plan is left for advertising, announcement or uselessness, even the VK site works according to this principle, with what help to place the template in the center, add indents on the sides?

Answer 1

It would also be possible to open the source code and see how it is implemented.