Hi as per your blog article https://osclasspoint.com/blog/osclass-create-child-theme-b21  I did all the changes, but still, I am facing an issue on-site.
could you please check that where is the issue?

this is the code I pasted in function.php

function gam_child_custom_css() {
 osc_enqueue_style('style-child', osc_current_web_theme_url('css/style-child.css'));
}

osc_add_hook('header', 'gam_child_custom_css')
error; It was reflecting on the page header http://prntscr.com/shrdqs
using gamma theme

You need <?php and ?> tags in php file

You need <?php and ?> tags in php file

Done Thank you