This is how you can change your site status easily. Change site status to "on" or maintenance mode with easily. Just admin can saw the website. Normal users, guests, visitors got 503.
Do not copy paste files. Just copy codes and past them to related section. After all files are done if you can't run this. write composer dump-autoload in terminal and you are done.
If you find any bugs or errors please send me email. [email protected]