Disk Utility is Apple's go-to macOS app for finding and repairing common disk errors, but if it's your Mac's internal disk that's the problem, then your Mac might not even start up into macOS.
The First Aid feature in Apple’s Disk Utility (/Applications/Utilities) represents one of the oldest and most helpful repair utilities available for your Mac. But ...
A step-by-step guide to fixing a black screen on MacBook Pro or an external monitor.