About sitemap xml generation

Dear support,
I am trying to put rank-math.php file into my child theme but it does not generate page-bn-sitemap.xml and page-en-sitemap.xml. it always show page-sitemap.xml. I have two languages in this website and powered by Polylang. One Language is Bangla and another one is English and Bangla is the default language.
The code is here:


<?php

/**

* Rank Math + Polylang Multilingual Sitemap Fix

*/

defined( 'ABSPATH' ) || exit;

/**

* Force load early

*/

add_action( 'init', 'rmppl_register_multilang_sitemaps', 5 );

function rmppl_register_multilang_sitemaps() {

if ( ! function_exists( 'pll_languages_list' ) ) {

return;

}

$languages = pll_languages_list();

if ( empty( $languages ) ) {

return;

}

// Register per-language post/page sitemaps

add_filter( 'rank_math/sitemap/post_types', function( $post_types ) use ( $languages ) {

foreach ( $languages as $lang ) {

$post_types["post-{$lang}"] = [

'name' => "post-{$lang}",

'object_type' => ['post'],

'query_var' => [

'post_type' => 'post',

'lang' => $lang,

],

];

$post_types["page-{$lang}"] = [

'name' => "page-{$lang}",

'object_type' => ['page'],

'query_var' => [

'post_type' => 'page',

'lang' => $lang,

],

];

}

return $post_types;

});

}

/**

* Correct URLs inside RankMath sitemap entries

*/

add_filter( 'rank_math/sitemap/entry', function( $url, $post ) {

if ( function_exists( 'pll_get_post_language' ) ) {

$lang = pll_get_post_language( $post->ID );

if ( $lang ) {

$lang_home = pll_home_url( $lang );

$url = $lang_home . str_replace( home_url( '/' ), '', $url );

}

}

return $url;

}, 10, 2);

How to fix it?
Thanks