Redirection apache vers nom de domaine

Bonjour à tous,

J'ai acheté un VPS et j'y ais mis mon Prestashop, j'ai relier le DNS de mon nom de domaine à mon VPS mais quand je met le nom de mon site internet j'arrive bien sur mon VPS mais l'URL ce change et deviens l'adresse IP de mon VPS, j'ai fait cette configuration dans les sites-available de apache :

__
_# The ServerName directive sets the request scheme, hostname and port that_
_# the server uses to identify itself. This is used when creating_
_# redirection URLs. In the context of virtual hosts, the ServerName_
_# specifies what hostname must appear in the request's Host: header to_
_# match this virtual host. For the default virtual host (this file) this_
_# value is not decisive as it is used as a last resort host regardless._
_# However, you must set it for any further virtual host explicitly._
_ServerName www.mysite.com_

_ServerAdmin contact@mysite.com_
_DocumentRoot /var/www/html/_

_# Available loglevels: trace8, ..., trace1, debug, info, notice, warn,_
_# error, crit, alert, emerg._
_# It is also possible to configure the loglevel for particular_
_# modules, e.g._
_#LogLevel info ssl:warn_

_ErrorLog ${APACHE_LOG_DIR}/error.log_
_CustomLog ${APACHE_LOG_DIR}/access.log combined_

_# For most configuration files from conf-available/, which are_
_# enabled or disabled at a global level, it is possible to_
_# include a line for only one particular virtual host. For example the_
_# following line enables the CGI configuration for this host only_
_# after it has been globally disabled with "a2disconf"._
_#Include conf-available/serve-cgi-bin.conf_
__
_ Order allow,deny_
_ Allow from all_
_ # New directive needed in Apache 2.4.3: _
_ Require all granted_
__
__

Mais rien n'y fait j'ai toujours le même problème, si quelqu'un peu m'aider ce serais super :) Merci d'avance