Theme automatically inserting “more” tag on every post

In your archive.php file, you would want to replace this:

<div class="entry-content">
<?php colabs_custom_excerpt(); ?>
<p class="more">
<a href="https://wordpress.stackexchange.com/questions/105195/<?php the_permalink() ?>">
<?php _e("More","colabsthemes"); ?>
</a>
</p>


With this

<div class="entry-content">
    <?php the_excerpt(); // or the_content(); ?>
</div><!-- .entry-content -->

The theme creator is MANUALLY inserting the more button (as you can see). You could just remove the paragraph containing the More button, or replace their custom function with the native functionality (both given).

If you plan on updating your theme ever (which I recommend you do), I strongly recommend creating a child theme, which is explained thoroughly here, and do any file/style changes there, instead of the theme itself. Just copy over the files into the child theme and edit there. This way, you won’t lose any changes when you update your theme!