Whats the native viewer, that is working in every OSX for viewing images/video when the space bar is pressed?
And how can the user set it to view all kind of videos (.mkv .mpg .avi) and images (.psd )?
Quick Look.
That's the native file viewer for macOS. It doesn't support every file type that you might use.
But, it supports a variety of plug-ins that can support a lot of other formats.
There's some good info here about adding new plug-ins to your Mac system.
