Storyline doesn't track time. You'd need JavaScript to tell the user their total time to complete the course. (Or just tell them to look at their watch at the beginning and end of the course. 😆)
You could use a number variable to count how many questions someone answered correctly the first time. At the end, it'd be easiest to simply show that variable (for example: "You answered [#] out of [#] correctly the first time.") Otherwise, you'd need additional triggers to calculate the percent.
Also use T/F variables to track whether it's the user's first time through each scenario. Exactly how and where you adjust the variables will depend on how your scenarios and navigation are set up.
Here are some resources that might help: