look at the last function, i have ******* next to the problem. The array need some more information. I don't know what to add.
I want to divide the values inside the array by 5, i just can't access the info
If the compilation fails due to code that the compiler does not understand, then the compiler gives an error message. One compiler says this about your code:
In function 'char getChoice()':
44:17: warning: statement has no effect [-Wunused-value]
In function 'void displayResult(char, double*)':
53:26: error: invalid operands of types 'double*' and 'int' to binary 'operator/'
53:8: warning: unused variable 'avg' [-Wunused-variable]
It does point to line 53 (just like you did) and says that you have there double* and int operands.
You have testScores / 5, where 5 is indeed int and testScores is double  according to line 47.
No disagreement there.
Learn to read the compiler messages. Learn to show them too.
Look at lines 27-30 of your code. There you do access each element of the array, don't you?