Search function

A link to your site would be helpful, as per WordPress Codex > Forum Welcome > Include as Much Information as Possible

Hello,
So, you want full-width in all pages, right?
If this is the case, then Connect with your FTP credentials -> Go to your site->wp-contents->themes->Select your activated theme->page.php
Then change

<div id="primary" class="content-area col-md-9">

to

<div id="primary" class="content-area col-md-12">

and in line no 34 remove the line

<?php get_sidebar(); ?>

You will have to use FTP to delete/update themes and files.
Watch: https://www.youtube.com/watch?v=_nDQz1JQfYA

Thanks!!