Mac – External Seagate harddrive suddenly not mounting nor responding to Diskutil

In short: has anyone tips to save my external hard drive or suggestions based on the extended explanation below?

Last week, I plugged my Seagate 2TB Backup Plus Portable Drive into my Macbook Pro like usual. The drive mounted and became visible in the finder, however it was only showing some folder and did not show files when I went clicked further. I removed the drive with the idea that plugging it in again would do the trick. However, this is where the drive stopped mounting.

I opened Disk Utility, and found the external hard drive being grayed out with not its own name. I tried to mount, did not work. I tried the First Aid, it gave back:
Control or recovery failed
The second try, it gave: Control or recovery failed (-69845)
Both with endcode file system being 8.

I didn't yet update my macOS to Catalina, so I did that before trying again. After updating, Seagate BUP Slim appeared as name. This wasn't its name before the struggles, but showed some progress.

I moved on to the Terminal, which tells me this:

/dev/disk2 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *2.0 TB     disk2
   1:                  Apple_HFS                         2.0 TB     disk2s1

I tried multiple commands from Diskutil. Diskutil info gave me:

MacBook-Pro-van-Marc:~ Marc$ diskutil info /dev/disk2
   Device Identifier:         disk2
   Device Node:               /dev/disk2
   Whole:                     Yes
   Part of Whole:             disk2
   Device / Media Name:       BUP Slim SL

   Volume Name:               Not applicable (no file system)
   Mounted:                   Not applicable (no file system)
   File System:               None

   Content (IOContent):       FDisk_partition_scheme
   OS Can Be Installed:       No
   Media Type:                Generic
   Protocol:                  USB
   SMART Status:              Not Supported

   Disk Size:                 2.0 TB (2000398933504 Bytes) (exactly 3907029167 512-Byte-Units)
   Device Block Size:         512 Bytes

   Read-Only Media:           No
   Read-Only Volume:          Not applicable (no file system)

   Device Location:           External
   Removable Media:           Fixed

   Solid State:               Info not available
   Virtual:                   No

Some other tries to get my Seagate up and running:

MacBook-Pro-van-Marc:~ Marc$ diskutil verifyvolume /dev/disk2
Error starting file system verification for disk2: Invalid request (-69886)

MacBook-Pro-van-Marc:~ Marc$ diskutil repairvolume /dev/disk2
Error starting file system repair for disk2: Invalid request (-69886)

MacBook-Pro-van-Marc:~ Marc$ diskutil verifyvolume /dev/disk2s1
Started file system verification on disk2s1
Verifying file system
Volume is already unmounted
Performing fsck_hfs -fn -x /dev/rdisk2s1
Checking Journaled HFS Plus volume
Checking extents overflow file
Checking catalog file
The volume   could not be verified completely
File system check exit code is 8
Restoring the original state found as unmounted
Error: -69845: File system verify or repair failed
Underlying error: 8

MacBook-Pro-van-Marc:~ Marc$ diskutil repairvolume /dev/disk2s1
Started file system repair on disk2s1
Repairing file system
Volume is already unmounted
Performing fsck_hfs -fy -x /dev/rdisk2s1
Checking Journaled HFS Plus volume
Checking extents overflow file
Checking catalog file
The volume   could not be verified completely
File system check exit code is 8
Restoring the original state found as unmounted
Error: -69845: File system verify or repair failed
Underlying error: 8

MacBook-Pro-van-Marc:~ Marc$ diskutil mount /dev/disk2s1
Volume on disk2s1 timed out waiting to mount

MacBook-Pro-van-Marc:~ Marc$ diskutil mount /dev/disk2s1
Volume on disk2s1 timed out waiting to mount

MacBook-Pro-van-Marc:~ Marc$ diskutil mountDisk /dev/disk2s1
One or more volume(s) failed to mount

MacBook-Pro-van-Marc:~ Marc$ diskutil unmountDisk /dev/disk2s1
Unmount of all volumes on disk2 was successful

MacBook-Pro-van-Marc:~ Marc$ diskutil eject /dev/disk2s1
Volume timed out while waiting to eject

MacBook-Pro-van-Marc:~ Marc$ diskutil mountDisk /dev/disk2
One or more volume(s) failed to mount

MacBook-Pro-van-Marc:~ Marc$ diskutil mountDisk readOnly /dev/disk2
One or more volume(s) failed to mount

MacBook-Pro-van-Marc:~ Marc$ diskutil unmountDisk /dev/disk2
Unmount of all volumes on disk2 was successful

MacBook-Pro-van-Marc:~ Marc$ diskutil eject /dev/disk2
Volume timed out while waiting to eject

MacBook-Pro-van-Marc:~ Marc$ ps aux | grep fsck
Marc              3352   0,0  0,0  4277496    680 s000  S+   12:35am   0:00.00 grep fsck

MacBook-Pro-van-Marc:~ Marc$ sudo kill -9 3352
Password:
kill: 3352: No such process

So, I am running out of possible options to fix this problem. I tried Single User mode, as introduced here: http://osxdaily.com/2013/08/07/how-to-repair-a-mac-disk-with-fsck-from-single-user-mode/ and https://www.howtogeek.com/236978/how-to-repair-disk-and-file-system-problems-on-your-mac/. It told me that the permission was missing, so this didn't help much.

Any tips/advise left what to try? I'm scared that my external hard drive is dying and I'm past the point of rescuing it.