Does Samsung has a feature like second space in Xiaomi?
UPDATE: there are apps for isolating environment and e.g. hiding other apps. Check Island.

Unfortunately, lots of Android capabilities are limited by producers - that's the case, too. According to this link on Reddit, people are searching, but with no success. The only devices are tablets, described e.g. here on Samsung Support page for Galaxy Tab S.

Of course you can enable multi-user functionality by modifying system files, but mostly that's not the way a standard user like - warranty issues, triggered Knox, disables access to S Apps... essentially, lots of problems.

So, to sum up - without modifications, it's impossible on Samsung smartphones to enable multi-user functionality. Root your phone, and then you'll be able to turn on multi-user, but keep in mind that rooting your device comes with lots of pros and cons.