Hi Lola! It's been quite long since I've worked on this project, and the code for the systems in this project were not up to par. Currently, I've improved a lot! I could try to explain a simple way of doing it, but making an inventory from scratch is not easy at all. I'd recommend following guides online, and even perhaps on Udemy. Currently, I'm working on an inventory system for the Unreal Marketplace. I've been working on it for ~2 weeks now.
Sadly you cannot save Objects. However, you can convert the object's data (the variables it holds) to a struct, then save the struct. When loading, you can load that struct, break it, and create necessary objects using the data saved inside your struct. You can also add me on Discord (@isikdev), I'll try to guide you a bit.