to see what is actually happening, add a function call:
oops, nothing seemed to have happened. And why is that? Because of this line:
for c in range(len(text) -1, 0):
go from 6 till 0. Well, 6 is already greater then zero, so this for loop will never execute, you might want to pass in a 3rd argument, to indicate your loop should be taking steps of -1:
for c in range(len(text) -1, 0,-1):
you might also want to change the second argument to -1, currently 0 (your first letter) is not included in the loop.
This should help you getting closer to your goal, if you need further help, post an updated version of your code, let me know you need further help, but i highly recommend to try again first. Maybe include some print statements inside the for loop, so you can actually see what is happening?