Hello,
There are a few options to do this, The simplest option would be to have a separate site for each language and create a static HTML page for the main URL with a button that sends them to one or the other. You can also use WordPress multisite for this, however, this is not recommended unless you are extremely familiar with the under workings of WordPress and are comfortable modifying and writing your own code. Alternatively, instead of having separate areas for users, you could use a plugin that translates the sites for the users and lets the user choose which language they want such as this plugin.
Best Regards,
KyleM