Trouble with foreign keys

[Else Novac]

In my ER diagram, I have a big table called "EVENT" that roughly looks like this:

EVENT_ID: INTEGER

USER_ID: USER

EVENT_TYPE: VARCHAR

SCREEN_ID: SCREEN

BUTTON_ID: BUTTON

TIMESTAMP: DATETIME

The USER table contains user data, the BUTTON table contains the name and the location on screen of the button. Event types are things like viewing a screen or clicking a button.

There are various categories of screens. One of them is called "Lessons", which contains more "Exams", each "Exam" containing more questions. So my SCREEN table (1:1 relationship with itself) looks like this:

SCREEN_ID: INTEGER

SCREEN_TYPE: VARCHAR

TIME_ON_SCREEN: INTEGER

SCREEN_URL: VARCHAR

PREVIOUS_SCREEN_ID: VARCHAR

PREVIOUS_SCREEN_URL: VARCHAR

There is a 1:M relationship between SCREEN and LESSON, a 1:M relationship between LESSON and EXAM, and a 1:M relationship from EXAM to QUESTION.

**The problem is, a single question contains more screens because first it shows the question and after I answer an explanation follows. So even if the question ID is the same, the screen ID changes.** How do I represent this relationship in the diagram and what happens to the SCREEN_ID key? Will it become a foreign key in QUESTION?