Спасибо всем кто морально был со мной))
если кто упростит будет интересно!
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<div id="post-nav" class="p-border">
<?php
$link = get_the_permalink();
$slugs = parseCatPostURL($link);// тут просто выдираю название категории! простейший метод на explode()
$current_category = get_category_by_slug($slugs);
$g=get_the_ID();
$t=$current_category->term_id;
$posts = $wpdb->get_results("SELECT `ID`,`post_date`,`slug`, `post_title`,`post_date`, `post_content`
FROM `wp_terms` AS `t1`
INNER JOIN `wp_term_taxonomy` AS `t2` ON t1.term_id=t2.term_id
INNER JOIN `wp_term_relationships`AS t3 ON t2.term_taxonomy_id=t3.term_taxonomy_id
INNER JOIN `wp_posts` AS t4 ON t4.ID=t3.object_id
INNER JOIN `wp_postmeta` AS t7 ON t4.ID=t7.post_id
WHERE t2.taxonomy='category' AND t1.term_id={$t} AND t4.post_status='publish' AND t4.ID<{$g} and meta_value in (SELECT meta_value FROM `wp_postmeta` WHERE `post_id`={$g} and `meta_key`=\"_category_permalink\")
ORDER BY t4.post_date DESC
LIMIT 1");
if (count($posts) > 0) {
?>
<div class="post-previous tranz p-border">
<a href="<?php echo the_permalink($posts[0]->ID); ?>
" title="<?php echo $posts[0]->post_title ?>">
<i class="fa fa-chevron-left" aria-hidden="true"></i>
<?php echo $posts[0]->post_title ?></a>
</div>
<?php
}else{
?>
<div class="post-previous tranz p-border">  </div>
<?php
}
$posts = $wpdb->get_results("SELECT `ID`,`post_date`,`slug`, `post_title`,`post_date`, `post_content`
FROM `wp_terms` AS `t1`
INNER JOIN `wp_term_taxonomy` AS `t2` ON t1.term_id=t2.term_id
INNER JOIN `wp_term_relationships`AS t3 ON t2.term_taxonomy_id=t3.term_taxonomy_id
INNER JOIN `wp_posts` AS t4 ON t4.ID=t3.object_id
INNER JOIN `wp_postmeta` AS t7 ON t4.ID=t7.post_id
WHERE t2.taxonomy='category' AND t1.term_id={$t} AND t4.post_status='publish' AND t4.ID>{$g} and meta_value in (SELECT meta_value FROM `wp_postmeta` WHERE `post_id`={$g} and `meta_key`=\"_category_permalink\")
ORDER BY t4.post_date ASC
LIMIT 1");
if (count($posts) > 0) {
?>
<div class="post-next tranz p-border">
<a href="<?php echo the_permalink($posts[0]->ID); ?>
" title="<?php echo $posts[0]->post_title ?>">
<?php echo $posts[0]->post_title ?> <i class="fa fa-chevron-right" aria-hidden="true"></i>
</a>
</div>
<?php
}else{
?>
<div class="post-next tranz p-border">  </div>
<?php
}
?>
</div>
