What is 5 divide by zero? but the answer is not zero?

5 divide by zero is Undefined

That’s right.   The answer is not zero.   In fact, there’s no answer at all,
simply because there’s no question.   In math in general, division by zero
is "not permitted", and if people start talking about it, the answer is called
"indeterminate". that means vague, and can’t be determined.

Division is repeated subtraction.   6 divided by 2 means:  "How many times
can you take 2 away from 6 before the 6 is all used up and gone?", and the
answer is: 3 times and then it’s gone.  

So the question is really asking:  "How many times can you take zero away
from 5 before the 5 is all used up and gone?".  There’s no answer, because
no matter how many times you take away zero, you can never use up the 5.

One more comment on the subject:  Save your question marks.   One is plenty.