Sorry, I can only read a little French and can write none, so I’m gonna answer in English, as best I can, and hope you’re able to get what you need out of it from Google Translate. (I got some Google Translate help understanding your questions, and still am not certain I understand them all.)
Est ce je pourrai migrer des hébergements cpanel vers ce seveur grave à virtualmin?
Yes. We support migrating from cPanel. It usually Just Works, and if you run into problems we’re usually able to fix it or guide you to working around it.
Que veux vraiment dire "Up to 10 domains on one server" ? Ca veut dire qu'on peut créer des serveurs illimités? et que chaque serveur peut contenir 10 domaines addon?
No. Each Virtualmin license is for one (1) server. If you have multiple servers (or virtual servers) you need multiple licenses. If you use Virtualmin GPL, there are no server or domain limits. Only the Professional version has domain limits and is licensed per server.
Pour la version GPL, est ce qu'on peut autant de compte pour chaque hébergement? Du genre, on crée un compte + nom de domaine et le compte est autonome pour créer ses BDD, FTP, EMAIL et autres .....
Virtualmin GPL has no account limits. The difference between Pro and GPL is in the number of Install Scripts (100+ in Pro vs 7 or 8 in GPL), priority support in our issue tracker, some extra third party service integration (for things like backups and such), reseller account support (which can also be used for departments or whatever kind of delegation suits your organization), a few other little bits and pieces.
A quoi sert un compte revendeur? Donner la possibilité à des comptes de créer des serveurs?
Yes. Reseller accounts (only available in Pro) provide an additional account type, which can be used to grant limited administrative privileges to semi-trusted users. They can create domains and perform management tasks on the domains they create. Some of our customers use them for departments, one of our university customers uses it to allow professors to create domain accounts for their students, etc. It’s pretty flexible, and allows for a variety of levels of delegation (you can grant more or fewer capabilities to the reseller, based on requirements).
Avez-vous la possibilité de nous aider à l'installer sur le serveur? Est ce qu'on peut l'utiliser pour créer des VPS?
We provide an installation service for $50, but we encourage you to try the installation yourself (we don’t like taking money for something that most people can do without any help, but we also can’t do it for free, as it just takes too much time…so we’ve made the install really easy). It’s very, very, very easy, and should Just Work on any supported distribution. I made a video about it here: https://www.youtube.com/watch?v=u89HJ0pz8bg
Virtualmin does not manage VPS or virtual machines. We offer Cloudmin (GPL and Pro) for creating and managing virtual machines or VPS. Virtualmin is a web hosting control panel, it has no awareness of virtualization.
Est ce qu'on peut vraiment tout faire? mail / ftp / gestion de fichiers / backup / cron / selection php / etc ....
Yes! Virtualmin does a lot (some would say too much, because it can be intimidating with all of its options and configuration).
Avez-vous un serveur dédié pas trop cher à nous conseiller?
There are a lot of good ones, and Virtualmin runs well on many of them. We test occasionally on the following and can recommend them: Digital Ocean, Vultr, Scaleway, Linode, RimuHosting. We also test occasionally on the major cloud providers, like AWS and Google Cloud, but beware they block mail ports, so you have to push mail out through a third party service, when using those providers; this may or may not be an issue for you. The major cloud providers are also rather expensive compared to the basic providers.