wider view of the website

Can you provide link to your site?

Sorry, I missed it: https://www.judo-vsg-fribourg.ch

One of the problems appears in some pages: the right bar is displayed under the content of the page…

You need to put this code either in your custom css or create a child theme and put it in the style.css of the child theme:

#content {
    width: 66.4%;
}
#secondary {
    width: 25.5%;
}

You can also use custom css plugin for that if your theme does not support custom css.

You can adjust the values as per your requirement.

Hello !

Sorry for the late answer… and good news: it works!
If I need a three column site, I guess the css should have #content #secondary and ?

Thanks again…

Thanks for the update.

For three column site, I am not sure what your theme is using but it is also generally used as #secondary for all sidebars.

Ok! Thanks for the info: maybe my website will need them both in the futur…

Okay no problem. When you have doubt regarding that, just use any Development tool (for example Firebug for firefox and Chrome Inspector for Chrome) to find out the original code required.