Try this:
<?php
$post_external_link = (get_post_meta(get_the_ID(), 'post_external_link', true)) ? get_post_meta(get_the_ID(), 'post_external_link', true) : '#';
$new_post_added = (get_post_meta(get_the_ID(), 'new_post_added', true)) ? '<span class="new_txt">' . get_post_meta(get_the_ID()...