I also create my first course. It takes too long than I planned before but I have some findings. Maybe they will help you.
1. I made every step that Udemy advise in their videos (https://www.udemy.com/official-udemy-insights-create-your-course-outline/learn/ and others). It was very helpful from my point of view.
2. I created notes for my course first. It is helpful to understand what you will deliver exactly.
3. I tried to create a video several times. Technically it is already good, I have a positive review from Udemy. However, I feel I need to improve the content in the video (not in the notes).
It means that the structure of the course I created with the notes (first lesson, second lesson, etc.) is not good when adding the videos. So my next approach is just to record every piece of information and then create a new structure of lessons.
Wish you success!