So, here is my story, and what happened:
I was doing something with disk partitions (WIN10) that i regret doing, but, it all was like this: I have a 2TB HDD, which i had divided in the past into 3 partitions D(100 GB),G[100 GB], H [the rest of 2 TB], and what i needed was to extend volume of D to at least 150GB, so i tried expanding volume from the empty space left from H (i backed up data from D to H), then, not exactly sure what happened next, somewhat fuzzy on the details due to the shock i suffered afterwards, but...what i do remember: i deleted the D partition, and tried to merge it back with H (and then create a brand new 150 GB partition D, which was what i wanted, but something else happened), merging "worked", but for some reason, on Disk Management screen i have seen TWO H partitions (the default one that had the rest of 2TB, and the other one, the former "D" was now "H"), as i have said, there were two H, instead of just one. So, what i wanted to do, is, that i selected the smaller 100GB H, and selected "delete partition", which ultimately deleted the whole H altogether, both 100GB one, and the "rest" of H. The G partition, and all of the content remained as is, unharmed and in one piece.
After this happened (and a lot of panic), i googled as much as i can, tried looking up ways to recover these deleted files...that brought me to a software "easeUS", which i tried, and in the end, after several hours, it was not able to fix this. Day after, i tried looking up different solution, and i found out about the "TestDisk", namely, this guide right there and i followed it to every detail: https://www.techsupportforum.com/forums ... J57Ixy_7q8
So, i did that, restarted PC, and i was quite surprised how quickly and effectively the TestDisk worked. But the outcome was not what i expected.
When i went to check HDDs, and there was just ONE hard drive letter (excluding my boot C drive, which was completely unaffected by this whole series of events), that being said, the whole 2TB HDD, there was only one partition, which had letter D on it. I checked contents of this D drive, and i have found literally ALL the lost data which used to be in the H partition.
However, i dont know WHY exactly, but all the content from the previously unharmed G partition were completely gone.
And this has brought me here, to ask if there is any way to recover the contents of the G partition after what happened.
Of course i tried looking up solutions, however i did not find any similar problems that would be this specific...like...TestDrive worked successfully, recovered data, but deleted other data?
TL;DR I have accidentally deleted wrong partition, used this tool, which helped me recover all the data i have lost, however, for some reason, it has completely deleted previously unharmed partition that i would really like to get back.
Also, a very big thanks to the developers of this application. Even if i loose the G partition forever, at least i have recovered majority of my lost data back. This app did more in less time than "easeUS" did in numerous hours, and even that did not even recover data correctly.
Edit: I have "solved" the problem
by using the "easeUS" - recovering the data from the former "G". Although very small amount of the data was corrupt, majority of it (approx 98%, i could say) was okay and i managed to replace the missing few % with new files.