Hi, Darya.
I think it's good that you approach this with skepticism. I think it's a good thing to have when it comes to diving and the right attitude for it; if you are ever unsure about something, ask questions, or don't follow through with it. It's a great example of not diving because something doesn't feel right. You don't have to give a good reason to not dive.
Back to your original question. The pool sessions are practical skills that you will need to know how to do in the ocean. There isn't an overwhelming amount that you have to learn and you will get to practice it many times in the pool. Most students that I have seen go through the course find that the pool session is enough for execution in the ocean. I do suggest that you schedule your ocean and pool days not too far apart so that the skills are still fresh in your mind, as is the feeling of being underwater if that is your first time.
For e-learning (online), this is mostly theory and also about procedures, what things are, how they work, but aren't substitutes for learning in person. They complement and will help build a foundation for the skills that you will also be going over in the pool.
For the vast majority of students, this is enough time and is good but of course, individual learning styles and rates differ and if you feel that at the end of the session, you need more, you can always speak with your instructor or the dive shop and schedule further time, perhaps one on one.