Structs don’t get individual getters/setters – you need to Break Struct and Make Struct to update them.
If you want the individual attributes to be editable, you need to make your Attributes object be a UObject. For this case, you probably actually want to make it an UActorComponent.
And, honestly, if you want to go deep into attributes, and are already OK with using C++, then you might want to look into the Gameplay Ability System. It takes a couple of hours to “grok” what it’s all about, and how it’s put together, but it’s a solution that solves a lot of problems, has a lot of features, and even works with networking.