Ok, that's much better. Your disk is indeed corrupted, but it looks repairable by following these instructions :-
Steps (please follow very carefully).
- Make a copy of the VDI (using the host OS) and set aside as a backup.
- In VirtualBox File|Virtual Media Manager, Release and then Remove the damaged VDI. Do NOT delete the physical file.
- Use VirtualBox to create a new VM - the details other than the disk don't matter since you will never run this VM. When you get to the disk creation step, create a disk which is exactly 245760MB (240GB). I will call this "the dummy vdi".
- With a hex editor, copy the first 512 bytes from the dummy VDI, and use it to overwrite the first 512 bytes of the damaged VDI.
- Still using your hex editor, edit the 4 bytes at file offset 388 (0x184). The new values should be "A8 3C 02 00".
- Save changes to the damaged VDI (after this it will no longer be damaged).
- In the settings for your original VM, select the controller, click the "Add hard disk" icon, and select your repaired VDI (which should still be in the original VM folder).
- The VM should now be repaired as far as VirtualBox is concerned.
Be aware that the VDI now has a completely new header, including a new UUID. I note that you are using a Grub boot - sometimes (rarely), Grub uses the UUID to identify the disk it needs to boot from, and will fail if the UUID changes. But, we can cross that bridge if and when we come to it.
You can delete that dummy/donor VM at any time, using the GUI of course.