Hard Drive Issues: Code 8. What does it mean?

Hello to all, I hope you are having a good day.

About a week ago my iMac would not boot up. So I took to the internet to figure out what the problem might be and came across some useful information.

I can boot up to Disk Utility and I see the hard drive and the space it has and everything but once I start running First Aid it tells me this:

Repairing file system.

• Checking Journaled "***" volume.
• Checking extents overflow file.
• Checking catalog file.
• Invalid key length
• The Volume "****" could not be verified completely.
• File system check exit code is 8.
• Updating boot support partitions for the volume as required .
• File system verify or repair failed.

Operation failed.

If i run it again, it bugs out and says there is no space on the hard drive. In the Info tab it says it can be Verified and Repaired but i have no idea how.

I have tried /sbin/fsck -fy in single user boot but it says that it cant do anything.

I restored it to the external hard drive I was going to use to back it up but it shows the same thing when i run First Aid.

So my questions are:

• Is It Fixable?
• Is there any way I can fix this problem without losing all the data stored on the HD?
• If not how can I recover all the data before I fix it?