Breadcrumb navigation is a list of links that provide an easy way for the user to navigate on your website. By default, WordPress does not come with the breadcrumbs functionality but you can add breadcrumbs to your website by using a 3rd party plugin.
Goedemorgen comes with a support for Yoast SEO breadcrumbs. Yoast SEO is a free WordPress plugin which is designed to make your website more SEO friendly. So, to display the breadcrumbs, you'll have to install this plugin.
Please note, you do not need to add any code to the theme in order to display the breadcrumbs. All what you need to do is to enable the breadcrumbs in your Dashboard. For more information please see Yoast SEO breadcrumbs documentation page (remember to skip the code part).