Error change permalink /page/2 wordpress? problem 404 !!!! Please help me!

Hello every one!

I have problem with 404 not found.PLEASE HELP ME!
I tried many of the ways from whole Internet.
original:
My target change this
HP https://www.something.com/page/2 TRUE
https://www.something.com/categories/page/2 TRUE
https://www.something.com/categories/subcategories/page/2 TRUE
https://www.something.com/author/page/2 TRUE

replaced by two code bottom:

HP https://www.something.com/new/2 FALSE
https://www.something.com/categories/new/2 TRUE
https://www.something.com/categories/subcategories/new/2 TRUE
https://www.something.com/author/new/2 FALSE

two things of which I have finished.
https://www.something.com/categories/new/2
https://www.something.com/categories/subcategories/new/2

It works correctly when I use these two codes.
First code in template directory/functions.php

add_action( 'init', 'my_custom_page_word' );
function my_custom_page_word() {
global $wp_rewrite; $wp_rewrite->flush_rules();
$wp_rewrite->pagination_base = "new";

Secondary code in wp-includes/class-wp.php 314 line

if (@$this->query_vars["name"] == "new")
{
$tmp_ar = $this->query_vars;
$this->query_vars = array();
$this->query_vars["paged"] = str_replace("/", "", $tmp_ar["page"]);
$this->query_vars["category_name"] = $tmp_ar["category_name"];
}

Next Two ways doesnt work,return 404 not found?

Do you any solution for this problem?

I am unlucky? I not found solution!

Thank you all for replies!