Font Awesome icons disappearing [closed]

It seems like that your pencil icon is being overwritten by your theme, see: http://www.omigretchen.de/wp-content/themes/venedor/css/plugins.css

Therefore, use the following code below to restore it:

.fa-pencil:before {
    content: "\f040";
}

Edit: Font Awesome 4.7.0 is highly outdated, as of this post, the latest stable version is Font Awesome 5.5.0

The following code will add Font Awesome 5 to you wp website and this will be placed in the footer.

I recommend you doing this with the Code Snippets plugin or putting this in your child theme’s functions.php

function add_footer_styles_font_awesome() {
    wp_enqueue_style('fontawesome5', 'https://use.fontawesome.com/releases/v5.5.0/css/all.css', array(), null );
};
add_action( 'get_footer', 'add_footer_styles_font_awesome' );

See documentation: https://fontawesome.com/how-to-use/on-the-web/setup/upgrading-from-version-4