As the error states at the end (I know, they can get pretty gross to with long paths in them), you are using backslashes instead of forward slashes on a #include. You use forward slashes ‘/’ for paths in #includes.
Go into the CharacterAI.cpp source file in your project and change the following:
#include "BehaviorTree\BehaviorTree.h"
to:
#include "BehaviorTree/BehaviorTree.h"