add_rewrite_rule. Please help!!!

I want to rewrite the URL below:

FROM:

https://example.com/test/portfolio/?pslug=plants

TO:

https://example.com/test/portfolio/plants

Details below:

With WordPress Permalink Settings set to “Post name”, my current portfolio URL is: https://example.com/test/portfolio/

My links on this page points to: https://example.com/test/portfolio/?pslug=plants

pslug is the custom parameter I added.

my functions.php

function add_query_vars($vars){
    $vars[] = "pslug";
    return $vars;
}
add_filter('query_vars', 'add_query_vars');

function add_portfolio_rules() {
    add_rewrite_rule('portfolio/([^/]+)/?$', 'index.php?page_id=117&pslug=$matches[1]', 'top');
}
add_action('init', 'add_portfolio_rules');

Please help!!! I have tried everything but nothing works.
Thanks!!!