#sidebar {
    background-color: #eaeaea;
    width: 18.5vw;
    height: 100vh;
    position: fixed;
    align-items: stretch;
}

<?php
/**
 * The Template for displaying job details
 *
 * Override this template by copying it to yourtheme/simple_job_board/single-jobpost.php
 *
 * @author      PressTigers
 * @package     Simple_Job_Board
 * @subpackage  Simple_Job_Board/Templates
 * @version     1.1.0
 * @since       2.2.0
 * @since       2.2.3   Enqueued Front Styles & Revised the HTML structure.
 * @since       2.2.4   Enqueued Front end Scripts.
 * @since       2.3.0   Added "sjb_archive_template" filter.
 */
get_header(); ?>

<img src = '<?php bloginfo('template_directory'); ?>/images/nieuwspagina-header.png' class="not-front-page-header" />

<div class="match-wrapper">

<?php
ob_start();
global $post;

/**
 * Enqueue Frontend Scripts.
 *
 * @since   2.2.4
 */
do_action('sjb_enqueue_scripts');

/*code continues....