I will use something like this
I added a variable to hold the list of random 3 questions out of the available questions. I created a list of 1 to the number of rows in the table and shuffled the list and then selected the fist 3.
This has now become my randomly selected questions.
In the Update quiz screen question function, I assign the first number in the list to the variable question and immediately remove it from the list to avoid duplicates.
You will need to check that the list of selected questions is not empty before attempting to read the next question.
Have Fun Thunking!