To implement such functionality, you will need to use variables.
You need to create 3 logical variables: Part2, Part3, and Part4, and initially assign them a value of false.
On the slide where Part 2 begins, you need to set the variable Part2 to true. (Do the same for Part 3 and 4.)
On the menu slide, you need to set the buttons that lead the user to Chapters 2, 3, and 4 to an inactive state. And assign triggers: when the slide time starts, change the Part2 button to Normal state if the variable Part2=true. Similarly do this with the buttons for Chapters 3 and 4.