There were standard questions that I hear UN prospective applicants are encouraged to use the STAR (specific situation, task, action, and result) method to reply to. The questions are often like, can you share an example of when you've done X,Y, and Z? They will often use UN specific jargon which if you're coming from outside the UN can sound intimidating, but what they're asking is actually very simple and they make it sound like something really elevated.