The trash is just like a recycle bin in Windows. When you move file to trash, the file is not physically removed from your hard disk, instead, it is residing in the trash folder.
To bypass trash and delete file completely, you need to enable the ‘Delete’ command.
Go to Places -> Home Folder
At the top menu, choose Edit -> Preferences
Select the Behavior tab. Put a tick on the box that says “Include a Delete command that bypasses Trash”.
Now right click on the file that you want to delete, you will see a ‘Delete‘ option just below the ‘Move to Trash‘. Clicking on it will now delete your file from the hard disk.