Seagate external HDD (-69874)

Hello.

I was working on my Mac (I'm a graphic designer) and suddenly my external Seagate 1Tb drive wouldn't allow me to access it. Actually it completely froze my Mac.

After manually restarting my Mac I noticed that my External HDD, though working, it won't mount. It takes forever to show up on disc Utility. When it shows, it tells me that it won't mount. If I try using first-Aid it shows me this message:

Fixing damaged partition map.

The operation couldn't be completed. (com.apple.DiskManagement error (-69874) )

Operation failed...

Anyone knows of a way for me to access the content in the HDD? I need to at least recover any working files that I have stored there!! Otherwise... I just lost two months of work and I need to deliver it this week!!!

Basically the drive seems to be working but it won't mount. I tried resetting SMC and PRAM, but nothing worked.

HELP!!