Thanks for the hint. However, the following error message comes up after I have called the link.
1452 Cannot add or update a child row: a foreign key constraint fails (cot.r3frg_acym_user_has_list, CONSTRAINTr3frg_fk_acym_user_has_list2FOREIGN KEY (list_id) REFERENCESr3frg_acym_list(id) ON DELETE NO ACTION ON UPDATE NO ACTION)