Make sure to add in your Project both FN_Basic.cpp and FN_CoreUObject_functions.cpp
If you want to use engine functions (You are internal, WHY WOULDN'T YOU! haha) add both FN_Engine_functions.cpp and FN_FortniteGame_functions.cpp as well
Don't forget to complete the function GetGlobalNames() in FN_Basic.hpp and the function GetGlobalObjects() in FN_CoreUObject_classes.hpp