Is a 2014 Mac mini fully compatible with Sierra? I bought a 2014 late Mac mini today from a shop where it was a test device. It has been registered but I got it cheaper. My problem is: it has macOS Sierra installed on it, which runs very slow, and the finder seems to be messed up. It does not show any file content.

Mac mini specifications:


CPU: Dual-core i5 1.4 GHz
RAM: 4 GB
HDD: 500 GB


Are current Mac mini devices shipped with Sierra, or it has been upgraded from El Capitan? It has been registered in 15 May 2017. Is this model fully and sufficiently compatible with macOS Sierra?
I would suggest re-installing the latest macOS that was installed on your Mac, without upgrading to a later version. This can be accomplished by pressing and holding Command-R immediately after pressing the power button to turn on your Mac mini.

Source: https://support.apple.com/en-us/HT204904