I'd need FTP access and steps to get to the update or delete page live to debug this and tell you why it doesn't work and what settings need to be changed.
Trigger: whatever event you want to start the update or delete (usually a submit button press)
Lookup Column: Primary Key column for your table
Lookup Value: usually a url parameter using <?php echo($_GET["paramname"]); ?> ... could also be a hidden form element value if you want