Reinstall macOS
How I can reinstall macOS high Sierra by internet
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Start up from macOS Recovery
To start up from macOS Recovery, turn on your Mac and immediately press and hold one of the following combinations on your keyboard. Command-R is generally recommended, especially if you never installed macOS Sierra 10.12.4 or later… https://support.apple.com/en-us/HT204904#notupdated
Command (⌘)-R
Install the latest macOS that was installed on your Mac.
Option-⌘-R
Upgrade to the latest macOS compatible with your Mac.
Shift-Option-⌘-R
Install the macOS that came with your Mac, or the closest version still available.
Or...
Try installing this in Safe Mode, but not using Firefox...
https://itunes.apple.com/us/app/macos-mojave/id1398502828?mt=12
Safe Boot, (holding Shift key down at startup).