How to check the character is falling after jumping , 2D - C#

Hey everybody! Im new to unity , I used this c# code to rotate the character(45 ) , if it goes up(when using space button ) and after that goes down and rotate (-45) , but it doesn't work well ! do you know what should i change ? when it start to rotate , it doesn't stop ! using UnityEngine; using System.Collections;

public class Player : MonoBehaviour {

 public Vector2 jumpForce = new Vector2(0,300);
 bool isFalling;
 bool playerFalling;
 bool jumped;
 
 void Update () {

     if (Input.GetKeyUp ("space")) {
                     jumped = true;
                     rigidbody2D.velocity = Vector2.zero;
                     rigidbody2D.AddForce (jumpForce);
     if (rigidbody2D.velocity.y > -0.1 && isFalling == false ) {

                             transform.Rotate (0, Time.deltaTime * 45, 45, Space.World);     
                 }
             }
 
     if (rigidbody2D.velocity.y < -0.1 && jumped) {
                 isFalling = true;
                 transform.Rotate (0, Time.deltaTime * (-45), (-45), Space.World);

             }