Hello everyone, its Ivan. I've been extremely busy recently with trying to get everything to save by writing into the files. Since I've never done something like this before it was really tricky and it took a lot longer then it should have. But after many weeks of help I was finally able to get everything to saved in the game. For example in the gif below I will show the game saving the inventory and chest inventory.
As you can see after opening a chest and receiving an item and later reopening a game the item stays there. I've also done it for the chests as well.