Hello, i was wondering how i could add a simple backpack system, where if i “pick up” a backpack, i will have more inventory space 
Hello,
Backpacks are “inventory like” containers with an exception : they can’t have another backpack added in (or they can but … ^^) Use the same system you use for your inventory with or the same links than your inventory with environment or a link backpack / inventory only to reduce actions needed to implement (like for shortcut systems). In both cases backpacks is an item non stackable, recognized as any other one by your inventory but a container for any backpack.