(LWJGL) A new aproach

Well, i left school yesterday getting excited about working on my first game engine. I have input, a window manager, and an fps counter. Then (using thebennybox tutorial) I saw Vectors. The pythag theorem was simple for me, but the cosine took me several minutes to understand. After that he got into matrices. ArrayLists containing Ms, no way. I was confused and just stopped there. I know he has those side videos, but I’m not sure if I can handle this. I already know up to VBOs and loading 3D models with the coding universe, where do you suppose I continue?