My story is really long and complex. But basically, I had two partitions on my HDD, one VERY important, and one that is not so important. After trying to shrink the not-so-important one and expanding the VERY important one, somehow, my important partition became "unallocated". TestDisk found it, I tried to bring it back by changing it from D to L as stated in the TestDisk Step by Step. It gave me a "Partition: Write error" but according to this article, that error is "erroneous", so I restarted the machine as suggested. Upon checking my Disk Manager, I noticed that the important partition turned from "unallocated" to "free space" while everything else became "unallocated". Interestingly enough, the "free space" is 410GB just like the partition I tried to restore (Highlighted in image). I really don't mind the other partition being cone, I just need the one REALLY important one.
Here's a few images to illustrate:


I'm really not sure what the next step should be.
Thank you very much!