If you don't have a separate backup of your data, contact Apple's support services for next steps. If Disk Utility found errors that it was unable to repair, you may need to erase the disk and reinstall macOS. Repeat this step for each volume on the disk, then each container on the disk, then lastly the disk itself. After Disk Utility has completed the check, select the next volume or container above it in the sidebar, then run First Aid again.If you can't click the button, skip this step for the volume you selected.

Click Run or Repair Disk to check the volume for errors.From here, go to Contents > Resources and look for files ending in. Start by selecting the last volume on the disk, then click the First Aid button. To clear up space on your Mac, delete the ones you don’t need: Open a Finder window. Beneath it you should see any containers and volumes on it. The top disk in the side column is your internal disk.Choose View -> Show All Devices from the toolbar in Disk Utility.From the utilities window in macOS Recovery, select Disk Utility and click Continue.If prompted, select a user, then click Next and enter the password.Turn on your Mac and continue to press and hold the power button until you see the startup options window.On Macs powered by Apple silicon, such as the M1 MacBook Pro, the process is a little different, as described in the following steps. Download, install and launch Aiseesoft Mac Cleaner on your Mac. On Intel-based Macs, pressing the Command-R key combination immediately on booting invokes Recovery mode. Steps to clean up startup disk with Mac Cleaner Step 1. Fortunately, in such cases you can still get to Disk Utility from macOS Recovery. 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.

How to fix startup disk on mac