If you can share some code that I can copy-paste and you tell me what you did with it, then I can do as you did and see the problem. It becomes very easy to tell you what is wrong with it. If I have to reconstruct what you might have written and what you might have done and then tell you my opinion of how I feel about it, it becomes very difficult.
But the error you show means that something definitely went wrong, and can_do_quest/2 is not defined at all. I see other problems as well, for example Result is Level > ReqLevel is almost certainly an error?
PS: use markdown for code. See this post.