Hello @Counsellorjasmine, and welcome to the community! we are excited to hear you want to start creating courses with Udemy.
As @SharonRamel said, you can definitely create videos using your phone camera - we actually have a great support article with more information about this here. I'd also recommend submitting a test video to review the quality of your audio, video, and delivery. This is a free service to get your production basics right before you film your course.
For your second query, I suggest visiting our Marketplace Insights tool. This is a searchable page on your instructor dashboard that shows you data on student demand, search volume, and revenue for a particular topic.