How to do on the first level domain and the second - management through one CMS?

Question

CMS

The main domain is site.com and make another en.site.com, but managed through one CMS (Wordpress). The subdomain is the English version of en.site.com (this should also be some kind of plugin, since the menu and all design should be in English on en.).

Answer 1

most likely you need to make a second copy of the site on a subdomain

Answer 2

There are several options:
1) wp multisite
2) configure the server so that en.site.com looks in the site.com folder, but adds the en global variable

Answer 3

You should definitely pay attention to the multisite function (wp multisite). It allows you to work with subdomains.

Answer 4

If there is one WP CMS for 2 domains, then definitely through Multisite
If there is a CMS for each domain, then the simplest option is through plugins, for example MainWP Dashboard