problem with adding comments

Do you have a wp-comments-post.php in your WordPress install root directory?

yes

it’s in the public_html folder with pther WP files

It looks like your comment form is posting to a bad URL. /wordpress/wp-comments-post.php is not correct.

Replace action="/wordpress/wp-comments-post.php" with action="<?php echo get_option('siteurl'); ?>/wp-comments-post.php"

Thank you very much!