Yes, we can separate the users based on devices.
As we are the owner of the website need to aware of where traffic will come to our website. Maybe the visitor comes to our site through Desktop, Mobile, and Tablets.
The same person can visit our site to different devices but analytics count that a separate use rather than a single user. This is because google analytic only tracks devices, not people.
You can fix this problem with the help of cross-device tracking.
In this technique google analytics track user id with the help of device cookies. If the same ID detected in the browser cookies then it assumes it a single user on different devices.