No direct redirection

Hi, First of all thank you for this great plugin.

I have a multilingual website (EN and FR), and I use polylang for this.
When WP Fastest Cache is activated I have an indirect redirection which is the following:
http://vivialix3.16mb.com/
http://www.vivialix3.16mb.com/
http://www.vivialix3.16mb.com/en/

My question: is it possible to have a direct redirection from http://vivialix3.16mb.com/ to http://www.vivialix3.16mb.com/en/ ? It is the case when WP Fastest Cache is deactivated.

I try to go in the .htaccess and I think this lines (added by WP Fastest Cache) are causing the issue:
RewriteBase /
RewriteCond %{HTTP_HOST} ^vivialix3.16mb.com
RewriteRule ^(.*)$ http\:\/\/www\.vivialix3\.16mb\.com\/$1 [R=301,L]

But I have no notion of how to do correction in .htaccess
Thank you in advance for your answer.

Vivien