How to show all posts in category

A lot depends on your theme. If you are using a free theme, post a link to your site here and you may get more help.

I’m using the kubrick theme, I’ve just customized it.

https://www.animelava.com

So, any solution?

You should be able to make a copy of archive.php and change it at the top to look like this:

<?php
/**
 * @package WordPress
 * @subpackage Default_Theme
 */

get_header();
?>

   <div id="content" class="narrowcolumn" role="main">
      <?php query_posts($query_string . '&posts_per_page=-1'); ?>
      <?php if (have_posts()) : ?>

         <?php $post = $posts[0]; // Hack. Set $post so that the_date() works. ?>
         <h2 class="pagetitle">Archive for the ‘<?php single_cat_title(); ?>’ Category</h2>

         <div class="navigation">
            <div class="alignleft"><?php next_posts_link('&laquo; Older Entries') ?></div>
            <div class="alignright"><?php previous_posts_link('Newer Entries &raquo;') ?></div>
         </div>

         <?php while (have_posts()) : the_post(); ?>

Thank you.

If that worked for you, please use the dropdown at top right to mark this topic ‘Resolved’.

Sure thing, it works great! Thanks ^^

You are welcome!