Guided Feedback for Failed Exams in Storyline

First, you'll need to be comfortable using variables and trigger conditions. Here are some resources: 

• The Value of Variables
• User Guide: Working with Triggers (which includes a section about conditions)

Create a number variable for each topic/QB. 

To count incorrect answers, do this on every question in each bank: Add a trigger that adds 1 to the corresponding variable when the user clicks the Submit button with the condition that the correct answer ≠ (does not equal)* Selected. Be sure this trigger comes before the "Submit [interaction]" trigger. Something like this: 

For the feedback, you could show different messages based on which two QBs had the most incorrect answers. But what if there's a tie? 

I think it'd be simpler to show how many wrong they got in each category. That's as easy as inserting the variable references. And include something like "This shows the number of questions you answered incorrectly in each topic. Before retaking this exam, take time to review topics as needed." 

• If you insist on providing QB-specific feedback, this post might help: TIP: Track Responses to Custom Questions or Surveys | E-Learning Heroes

Note: If the user can retake the quiz and you want to provide updated feedback, you'll need triggers that set the variables back to 0 before they retake the quiz.

* It's more stable to use "≠ (is not) Selected" or  “≠ (is not) Visited" as a condition, 
instead of "= (is) Normal." As Hero Walt Hamilton put it: "Like us, the built-in 
states all think they are Normal." In other words, Normal underlies those states, 
and the "= Normal" condition doesn't always work as expected.

One more thing for future reference:  This Exchange Best Practices section is for general questions about eLearning. You’re asking how to do something in the software. That type of question is a better fit in the Discuss Articulate Products section of the website. That's where those of us who regularly answer questions about how to use the software spend more of our time. And that's where more folks go to search for answers specifically related to Storyline, Rise, and other parts of Articulate 360.