how do you collect questions for persona? are they just random questions collected by the team?

Oftentimes a team will start with what are called proto-personas. You start with assumptions made from stakeholders based on some preliminary data collected via research or feedback. Again, proto-personas are based on assumptions. Their value is to allow a team to start designing and developing right away. You never want to let proto-personas sit for very long though. Once you have something to test, you'll want to revisit your personas frequently to get them right, as proto-personas are guaranteed to be flawed. That being said, even the personas that you feel are "right" should be updated over time as users needs and wants are ever evolving.

In regards to the questions that you form, you'll need to sit down and flesh out what your goals are first. What is the problem that you are trying to solve? How does it change the world or individuals' lives? Start writing up some stories (again assumptions) for individual user journeys that people have without your product. What needs do they need fulfilled? What problems do they face? Are their problems caused by other products? The lack of a product? The answers to these questions will help you to build more focused questions that you need answered by potential users. Sometimes the data you collect will help you to write even better, more focused questions and sometimes they help you form ideas for your first version of your product. In either case, the data you collect will help you to improve your proto-personas into personas that you feel more confident designing a product for.