Notice how the Next button calls GetQuestion even after procedure QuestionNumber has returned, regardless of whether or not QuestionNumber has opened another Screen.
The Score screen refers to TinyDb for its score, so this startValue is superfluous.
Your GetQuestion procedure does not check if the global QuestionNumber is still in range.
It also has a meaningless self-assignment of a variable to itself.
This is safer:
On the whole, making separate screens for seperate quizes is a mistake.
The questions and answers should be loaed from a File or spreadsheet somewhere.