If you don't understand those tutorials for LWJGL and how to work with the APIs, then move onto Unity. It makes zero sense to develop engines if you cannot understand a game library this early on. I also do not recommend even starting with openGL unless you're very familiar with the language and the basics behind how the API (openGL) works. It's important to understand why things work otherwise you wont be able to duplicate it in a more dynamic way from scratch as you grow.
Do yourself a favor, pick up C#, and stick to Unity. If your goal is to make games, there is no need to re-invent the wheel at the beginner level.