How do I restore download which was accidentally deleted from a mac mini?

To restore a deleted download on a Mac Mini, first check the "Trash" folder; if the file is there, right-click it and select "Put Back." If it's not in the Trash, you can use the built-in "Time Machine" feature to recover it, provided you have backups enabled. Simply open Time Machine, navigate to the Downloads folder, and select the version of the file you want to restore. If these options don't work, consider using a third-party file recovery tool.