Select Disk Utility from Installer menu.
In the left panel, select the volume you want to repair. In the right panel, click on First Aid tab.
Click on the Verify Disk button to begin a verification process.
Select Repair Disk to fix the problems of selected volume.
2. Time Machine
Following the initial backup of your entire Mac, Time Machine automatically makes incremental backups every hour, every day, copying just the files that have changed since your last backup. And it does this all in the background, so you can continue working while Time Machine is busy copying your files. Time Machine saves the hourly backups for the past 24 hours, daily backups for the past month, and weekly backups for everything older than a month.