How to reinstall the current version of macOS or downgrade it
Recovery reinstall, using an Installer app, or a bootable installer, or with an Apple silicon Mac in DFU mode? What the choices are, and how best to do it.
WordPress installer attack race
Startfähiges Installationsprogramm für macOS erstellen
Create a bootable installer for OS X
With OS X El Capitan, Yosemite, or Mavericks, you can use a USB flash drive or other removable media as a startup disk from which to install OS X. German guide → https://support.apple.com/de-de/HT201372