To put this in perspective:
Space the Harddrive is "showing as used"

Space actually seen when calculating all of it together:

=> about 600 GB seem to be "Lost" (they ARE on the disk however the files are not there, empty folders where files used to be).
I tried using testdisk which usually helped me in such cases:
[spoiler]

The problem now however is the reproted
"disk too small issue"
Is there any way I can copy ALL of the found files to another disk perhpas ?
I have another 4TB ready for migrating files over.
Except if there is a way to fix this without using that disk.
Thanks in advance to those of you who know more about testdisk than I do