NON OS (windows) files deleted/ hidden with OS uninstaller

I had a dual boot system with Windows 10 and Ubuntu 20.04. One partition was dedicated to keep files which could be accessed from both the OSes. Then I removed the windows by formatting the partition containing Windows however the entry was still available in Grub. So i decided to use OS-Uninstaller to uninstall windows completely. I downloaded and used the said utility in Ubuntu and it gave me a success message. However, after this I am unable to access files in the common partition. When I access the partition in Linux it shows me its full size with only around 500MB space used. When I access the partition using Windows diskmanagement (I installed windows again) it shows that around 50GB is used. Output of $sudo parted --list is as follows:

Model: ATA WDC WD10SPZX-22Z (scsi)
Disk /dev/sda: 1000GB
Sector size (logical/physical): 512B/4096B
Partition Table: msdos
Disk Flags: 

Number  Start   End     Size    Type      File system     Flags
 3      1077MB  262GB   261GB   extended                  lba
 7      1077MB  50.0GB  48.9GB  logical   ext4
 5      50.0GB  62.0GB  12.0GB  logical   linux-swap(v1)
 8      62.0GB  157GB   95.3GB  logical   ext4
 6      157GB   262GB   105GB   logical   ntfs
 4      262GB   1000GB  738GB   primary   ntfs            boot

My question is: Have i accidentally lost my files? or are those files somehow hidden? If deleted is there a safe way to recover those files?

I hope I have made myself clear. I am not attaching any logs because I dont know what is need to trouble shoot the issue.

Guidance will be highly appreciated.

Use Testdisk utility:

1. sudo apt -y install testdisk -- to install testdisk
2. sudo lsblk --for the partition name
3. testdisk -- in the terminal, to start the utility & go from there
4. When the entire process finishes and you are okay with the findings, press C to restore the recovered files at any directory of your choice.

Hope this helps.