Your domain model is wrong. A Teacher can have multiple qualifications and each qualification could be attached to multiple teachers. So imho this is a multiple – multiple relation. Same for Teacher and Event because the teacher can go to multiple events and I think that one event can have multiple teacher attending that event. If you set it up like this you can retrieve from the event the qualification and retrieve the teachers going to that event. You could also from the teacher retrieve its qualifications and then retrieve the upcoming events for that qualification.
I would solve it with an XPATH when you retrieve the events. Something like:
[Event_Qualification/Qualification/Teacher_Qualification/Teacher = [%CurrentUser%]]