Help me to update my website prestashop 1.6 to 1.7

Hello,

I try to update my website from prestashop 1.6 to 1.7.4.2 by FTP but I can't.
I created a safeguard of the version 1.6 on a file "OLD" on the FTP.
I charged the new files of prestashop 1.7.4.2 on the FTP.
I charged the old files of OLD on the root of the FTP:
/img
/upload
/download
and the file:
/config/settings.inc.php

Like here: https://www.prestashop.com/fr/blog/mettre-a-jour-ma-boutique-prestashop-1-6-vers-1-7

When I launch the update, nothing happen