I've got a LaCie HDD (3TB) which I cannot mount because there seem to be issues with the partition table, according to disk utility. I'm on a mac (Sierra, up to date). Disk utility can't repair it, but it lists the hdd. When trying to repair, disk utility says: "Repairing damaged partition table. Operation can't be completed (com.apple.DiskManagement error -69874.) Operation failed..." 

In Disk Utility it's listed as:  

ST3000DM 001-1CH166 Media, 3TB, not initialized  

Location: external  

Connection: USB  

Partition-table: not supported  

SMART-status: not supported  

Capacity: 3TB  

Number of sub-partitions: 0  

Type: Disk. Device: disk2 

The disk itself is formatted as Mac Journaled (GUID). My other HDD's have 2 partitions (according to testdisk the damaged disk has a Linux [L] & LBA [E] partition). Tried quick search and deep search on testdisk (it said something like filesystem was OK, partition table damaged. Don't know exactly though).  

Used testdisk to write a partition table, but that didn't change anything. Am hesitant to just press some options on testdisk, since I don't want to damage my files further and don't know what all those options do. 

The disk has data on it that I really need (when I found out it was corrupted, I just wanted to back the data up to another HDD.. ironic isn't it?), so it would be great if I could retrieve it. The files on it are mainly .PNG, .JPEG, .PSD and .CR2, some video formats and older/mobile image formats too. Think there's a time machine backup on it too. 

What should I do? Is there another option with teskdisk, or photorec?

PS: Yes, I know, back-up back-up back-up.  

PPS: I've tried contacting specialized businesses but those services are way to expensive for a student like me. Currently a demo of Data Rescue 4 is running to check what can be recovered, but heard that software like that can't give you back files like .psd, and since it's kind of expensive too I'm kind of hesitant to pay this much for something if it can't restore most of my files.

Testdisk wrote a new partition table after analyzing, as well as GParted, but both of those didn't work. Heard about photorec, but would it give me back all the files I have, or only files with specific extensions?