[נפתר] We change wp-admin URL without plugin

Background of the issue:
We want to change wp-admin login URL from default (wp-admin) to custom login URL without plugin. We change wp-admin URL with below solution: First of all, we went to the cpanel and change the name of wp-login.php file to wpadmin-customname.php. After that we changed all wp-login string in this file to the wpadmin-customname. In the last step we went to the wp-includes and edit general-template.php and changed wp-login URl. Every thing works fine and we can login to the dashboard with new URL (wpadmin-customname.php).

Symptoms:
This code works just for default language (Arabic) and if we change language to English, we can not login and get a 404 error.

Questions:
What should we do to change wp-admin URL to custom URL without plugin?