I have a serious problem with my TimeMachine external 8TB Seagate. It has been used as my TimeMachine disk. Did a full backup, installed lastest OS X from scratch and the external disk will no longer mount. My pictures are on this disk. Here are the commands I have run to try and fix this. I don't want to use DiskWarrior or any other Thirdparty software.

diskutil list
  /dev/disk0 (internal, physical):
      #:                       TYPE NAME                    SIZE       IDENTIFIER
      0:      GUID_partition_scheme                        *250.1 GB   disk0
      1:                        EFI EFI                     209.7 MB   disk0s1
      2:                 Apple_APFS Container disk1         124.7 GB   disk0s2
      3:       Microsoft Basic Data DEBIAN                  124.5 GB   disk0s3
      4:                 Apple_Boot Recovery HD             650.0 MB   disk0s4

  /dev/disk1 (synthesized):
      #:                       TYPE NAME                    SIZE       IDENTIFIER
      0:      APFS Container Scheme -                      +124.7 GB   disk1
                                    Physical Store disk0s2
      1:                APFS Volume OSX                     21.4 GB    disk1s1
      2:                APFS Volume Preboot                 22.9 MB    disk1s2
      3:                APFS Volume Recovery                512.0 MB   disk1s3
      4:                APFS Volume VM                      20.5 KB    disk1s4

  /dev/disk2 (external, physical):
      #:                       TYPE NAME                    SIZE       IDENTIFIER
      0:      GUID_partition_scheme                        *8.0 TB     disk2
      1:                        EFI EFI                     209.7 MB   disk2s1
      2:          Apple_CoreStorage Seagate                 8.0 TB     disk2s2
      3:                 Apple_Boot Boot OS X               134.2 MB   disk2s3

  /dev/disk3 (external, virtual):
      #:                       TYPE NAME                    SIZE       IDENTIFIER
      0:                  Apple_HFS Seagate                +8.0 TB     disk3
                                    Logical Volume on disk2s2
                                    784988D6-B233-4BFC-AB1C-45EA7FF24640
                                    Unencrypted

sudo fsck_hfs -l /dev/disk3
  ** /dev/rdisk3 (NO WRITE)
      Executing fsck_hfs (version hfs-407.50.6).
  ** Performing live verification.
  ** Checking Journaled HFS Plus volume.
      The volume name is Seagate
  ** Checking extents overflow file.
      Invalid leaf record count
      (It should be 190 instead of 192)
  ** Checking catalog file.
      Invalid sibling link
  (4, 318227)
  ** The volume Seagate was found corrupt and needs to be repaired.

sudo fsck_hfs -r
  ** /dev/rdisk3
      Executing fsck_hfs (version hfs-407.50.6).
  ** Checking Journaled HFS Plus volume.
      The volume name is Seagate
  ** Checking extents overflow file.
      Invalid leaf record count
      (It should be 190 instead of 192)
  ** Checking catalog file.
  ** Rebuilding catalog B-tree.
  ** The volume Seagate could not be repaired.