Lessons do not seem to be going in order

I'm taking the basic math course and I will get a shortlist of what I need to learn. I watch a few video's and the lessons skip ahead before I finish the lessons. For instance, I was working on adding and subtraction of positive and negative numbers and the next lessons were listed as multiplication and division of positive and negative numbers. Then for no apparent reason, I'm brought to the section related to exponents. I took a few lessons on exponents and again my lessons switched to something else. I feel I would learn better by finishing lessons before moving on to totally different lessons. Shouldn't I be learning in some kind of order? I can't keep track of what I'm learning. I hadn't even learned multiplication and division of positive and negative numbers which were listed as the lessons I would do next but suddenly my lessons skipped to exponents. I don't even know how to get back to the lessons which were skipped. While learning exponents most of those lessons were also skipped and I was brought to different lessons again. I can't learn anything this way. Shouldn't these lessons be taught in some sort of logical order?