We have created (without doing it on purpose) an event by asking for a recurrence (repeating event). It's a mistake... I would now like to delete this recurrence, how do I do this? knowing that in the "Repeat" menu of the event, the "End" field is mandatory... Thanks a lot for your help
Welcome to CiviCRM stack exchange. You can't get rid of everything to do with the repeat tab, but you can get rid of all but one occurence. If you go to manage events then you will see the recurrences listed separately and you can delete all but the first one (or whichever you want to delete). Its not quite the same as if you'd never set repeat, but as far as front end users (and in most respects back end users) it makes no difference.