content width ratio

Can you show us an example page that you want this applied to? In future try to avoid modifying the theme’s files, it’s bad practice.

Try adding this to your Child Theme style.css file:

@media screen and (min-width: 48em) {
    .page-two-column.has-sidebar #primary {
        width: 36%;
    }

    .page-two-column.has-sidebar #secondary {
        width: 58%;
    }
}

You haven’t put it in your Child Theme style.css file: http://kemenyseprok.hu.s5.webdigital.hu/wp-content/themes/twentyseventeen-child/style.css?ver=4.7

To make your life easier I would recommend picking either to use your Child Theme style.css file or Custom CSS theme option and not both.