Name change function

I would like to remove the concatenation of the first name and the last name of the students’ certificates. I would like to show only the first name, make an edit in the archives
class-woothemes-sensei-certificate.php and in class-woothemes-sensei-certificate-tempates, change the name’s visibility to:

// Get Student Data
			$user_id      = get_post_meta( $certificate_id, 'learner_id', true );
			$student      = get_userdata( $user_id );
			$student_name = $student->display_name;
			$fname        = $student->first_name;
			$lname        = $student->last_name;

			if ( '' != $fname && '' != $lname ) {
				$student_name = $fname;
			}

However, if there is an update to the plugin, if you lose these settings, could you help me include a function in the functions.php of my children’s theme? How can I insert a function in the file that changes this?