limit number of tags shown in tag.php

Been hitting a nail with this one as i’m very amateur with php. I have a loop in tag.php but it shows all posts with that tag – how can I limit the number to say, 5?

<?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>
    <h2 align="center">  <a href="<?php echo get_permalink() ?>"> <?php the_title(); ?>  </a> </h2>
    <?php the_content(); ?>
    <?php endwhile; else: ?>
    <h2>Woops...</h2>
    <p>Sorry, no posts we're found.</p>
    <?php endif; ?>
<?php wp_reset_query(); ?>