check for custom post type and pages
https://stackoverflow.com/questions/23363333/how-do-i-change-the-css-of-only-one-page-in-wordpress
https://wordpress.stackexchange.com/questions/169371/if-is-custom-post-type-archive-page
https://developer.wordpress.org/reference/functions/is_page/
<?php
if( is_post_type_archive('mg3_projects') ) { ?>
<link rel="stylesheet" type="text/css" href="<?php echo get_bloginfo('template_directory') . '/assets/css/normalize.css' ; ?>">
<link rel="stylesheet" type="text/css" href="<?php echo get_bloginfo('template_directory') . '/assets/css/layout.css' ; ?>">
<link rel="stylesheet" type="text/css" href="<?php echo get_bloginfo('template_directory') . '/assets/css/owl.carousel.min.css' ; ?>">
<link rel="stylesheet" type="text/css" href="<?php echo get_bloginfo('template_directory') . '/assets/css/owl.theme.default.min.css' ; ?>">
<?php } ?>
<?php
if( is_page('about-us') ) { ?>
<link rel="stylesheet" type="text/css" href="<?php echo get_bloginfo('template_directory') . '/assets/css/timeline.css' ; ?>">
<?php } ?>