Erase Macintosh hd

One can not Erase the macOS while it is operating. This document will help. Strongly suggest before attempting , make a Time Machine Backup AND Create a Bootable Installer of the version of macOS the computer is compatible with. One does not what to have a computer without any macOS on it and then try finding the way to reinstall.

mmgol wrote:

Hi. I want to clean install my MacBook Pro 2014 on disk utility and i cant erase my hdd. When I put the Erase button nothing happened

You can not repair/erase/re-install a Disk you are booted to.

How to reinstall macOS from macOS Recovery - https://support.apple.com/en-us/HT204904