Hey, i have a hard time knowing like finding the getNewItem() like ive never seen that before until I saw a function, where can I get a list of all of those •Sub-Functions• idk if thats what you call them.
You can check them on the PMMP GitHub repo (https://github.com/pmmp/PocketMine-MP) or you can use an IDE like PHPStorm and add PMMP source as a library and it can auto complete for you.
Perhaps you should know more about object-oriented programming. For example, in your main class it extends PluginBase, so you can find functions in the PluginBase class. getServer() returns a Server object, so you can go looking at the Server class. When you have a Player, it extends Human, which has a getInventory() method returning a PlayerInventory. Not all code are well-documented, but through looking at more places in the source code, you can understand better.