Answer 1

because you print out a string. you put:

print("x + y")

when it should be:

print(x + y)

Answer 2

To add to what's already been said:

line 5
if op == "+" :
^
IndentationError: unexpected indent

This error message tells you that the indent should not be here. In Python, indentation is how it can understand where your code blocks begin and end.

Remove the space behind each if/elif statement and it should be able to run. (Leave the print functions indented)