can’t remove sidebar for static pages

Try specifying width to content.page,post classes like width:980px;

Sorry, I don’t anderstand. I’m editing the page template file:
wp-content/themes/librio/page.php
Which bits of code in there shoud I change and how?

could you please post the URL ?

Of course! https://www.kalinga.se

You say that you want to set up some static pages without the sidebar, so I am assuming that some pages will still have the sidebar. Here is what I’d do:

1) Copy page.php to full_content.php
2) Add

/*
Template Name: FullContent
*/

to the top of the new page right after the <?php
3) Remove the sidebar including the whole div id=”sidebar”
4) Add a class to div id=”content” so that you have

<div id="content" class="full_content_width">

5) Add

div.full_content_width { width:100% }

to your style.php
6) Add your pages using the WP Pages->Add New panel selecting your new template as the template for the page– over on the right under ‘Template’.

Hopefully that will work. It should at least get you close.

You could add a switch to you existing page.php and avoid creating a new template file, but this way makes it easy to choose sidebar vs no-sidebar as you go along.

There is no style.php file. There is a style.css file but I cant see where the line div.full_content_width { width:100% } would fit in.