I wanted to clean my external disk that I use to back up my mac, but I didn't do it right... I deleted the folder 'Mac's Name' with my back ups, but the weird thing is that there is no extra free space on my external disk. So I learned that you have to delete your back-up within the Time Machine Interface. But I can't recover this folder from the trash can because of this message: "The operation can’t be completed because backup items can’t be modified."
If you haven't emptied the trashcan, then you can manually move the files back from the
/Volumes/<diskname>/.Trashes directory inside a terminal window
Note: You need to be root, so first
sudo su -
and then cd into the .Trashes directory, and use
mv * .. should move and make them available again