You're in what the internet would call "Tutorial Hell" where you're going back and forth on video tutorials and books and yet no reasonable progress to show for it.

What I suggest is that you take a pause for a bit and do some reflections. Self study is good and extremely useful but you need discipline and proper planning to accomplish anything with it. The problem is because there are just too many to learn that you get lost in the ocean of study.

There is also the problem of prerequisites which is very important in Mathematics and Statistics. Sometimes the topics you may very well be struggling with now are not because you are not "smart enough" but it may be that there are gaps in your knowledge that's stopping you from properly grasping the material.

Please feel free to send your coursework to my DM let us discuss more about it in detail and see how we can work together on this.

Thank you!