Maybe you want it to say ‘Lecturers’ and ‘Organizers’ instead?
You can change these names yourself and you make the change per event.
1. Open the event
2. Go to 'Collaborators' in the left menu and then select 'People' and/or 'Companies'.
3. Change the name by typing something else there.
Cannot edit? If so, it means that the event is published. In this case, you must first ‘Enable editing’ in order to change the name.