how to repair error: Cross Check : FSroot tree references extent (0x392/142 + 10) which is not present in the ExtentRef tree

One thing that is not commonly known is that when running Disk Utility and getting errors such as you did, the solution is often to rerun Disk Utility several times until it fixes the problem. If the problem persists and cannot be fixed and assuming that you do have a real issue, then I would reinstall the operating system.

Is this reported by Disk Utility?

Is data on it backed up elsewhere?

Backup your data if still accessible, if it hasn't been already.

Update any utility you are using. Do not use any optimizing tools. Mackeeper, Advanced Mac Cleaner, are actually malware, and should be removed. The only utilities I recommend for evaluating the health of a backed up hard drive are Binary Fruit, MicroMat, Prosoft, and Alsoft. Stay far away from Zeobit and Macpaw.

A reinstall of the operating system does not fix btree errors all the time. Some storage devices get permanently corrupted bits that when you reformat are simply locked out from editing so you can properly use the drive. Eventually drives can become so corrupt, it is impossible to install a new OS.

Solid State drives are less susceptible to corruption than platter drives, but not invulnerable.