Yes, of course! Until the day of your event, you can change anything you like. It will be visible within a few minutes in the app, even if the event has already been published.
However, on the first day of your event, you can no longer change your general event information (find it in Settings → Event). This includes information such as event name, logo, category, place, and description. Apart from this, you can still make changes everywhere.
Note: The first day is determined by the date, not the time when your first session starts.