The problem is your section variable:
myStepper.step(100); // turningthe motor to 25 steps to get 45 degree rotaion
Ignoring the fact that you're mixing up boolean values and LOW, the first time the button is pressed, section is false which happens to be zero, as is LOW, so the stepper steps and section is set to true (1). Next time the button is pressed, section isn't LOW any more and never will be again as you never change it, so the stepping portion isn't executed.
What is the section variable supposed to do?