Linux on My MacBook Pro - Want to erase Linux and reinstall macOS
Follow these instructions to erase and reinstall macOS:


  Start up from macOS Recovery
  
  
  macOS Recovery installs different versions of macOS depending on the key combination you use while starting up. Turn on or restart your
  Mac, then immediately hold down one of these combinations:
  
  
  
  2.Release the keys when you see the Apple logo or a spinning globe.
  
  Erase your startup disk
  
  If you need to erase your startup disk, follow these steps:
  
  
  Select Disk Utility from the utilities window of macOS Recovery, then click Continue.
  Select your device or volume in the sidebar of Disk Utility.
  Click the Erase button or tab.
  Complete these fields:
  
  
  Name: Enter a name for your disk, such as "Macintosh HD".
  Format: Choose Mac OS Extended (Journaled) or APFS.
  Scheme (if available): Choose GUID Partition Map.
  
  Click Erase to begin erasing your disk.
  When done, quit Disk Utility to return to the utilities window. You're now ready to install macOS.
  
  
  
  
  Install macOS
  
  
  Choose Reinstall macOS (or Reinstall OS X) from the utilities window.
  Click Continue, then follow the onscreen instructions. You'll be asked to select your disk. If you don't see it, click Show All Disks.
  Click Install. Your Mac restarts after installation is complete.
  
  
  If you erased your disk before installing, or you installed on an
  external drive or other new disk, your Mac restarts to a setup
  assistant.
  
  
  If you're keeping your Mac, complete the setup assistant with your own information.
  If you're selling or giving away your Mac, press Command-Q to quit the setup assistant without completing the setup steps. Then click
  Shut Down. When the new owner starts up the Mac, they can use their
  own information to complete setup.
  




More more information: What to do before you sell or give away your Mac - Apple Support