WordPress has a special built-in feature, multisite. Do you know what is multisite or what wordpress multiste refers to. ok lets explain
In wordpress you can create multiple websites using the same wordpress install, called multisite network. That mean by installing one wordpress on your server, you can run as many sites as you want
The best thing about wordpress multisite is that every site in multisite is as it is. it has the same folder structure, the same core files and the same code base.
That means installing a wordpress multisite network is just like a installation of a wordpress site and it is not complicated , and updation of multisite is exactly the same as update of any WordPress site