You'll do best, I think, if you can do as the assignment requires, and write from experience. The assignment asks you to write on:
on a situation you have observed or experienced which depicts effective or ineffective decision making and leadership
So, list all of the organizations with which you've been involved, not only workplaces but also sports teams, clubs, and the like. Then, for each one, think back over your experiences and observations. Can you recollect any instances of especially good or especially bad decision making? Especially effective or particularly poor leadership?
That process can help you decide on a situation to write about. That can lead to the formulation of a research question.