Slow Mo effect with Time.timeScale? Dont understand Lerp and Corutines...

I allready have a working code to achieve a slow mo effect... It falls down and then up- but, I think it can be made way cooler by someone who understands coroutines and lerp properly (this person is not me);

How could I implement an effect similar to this one by using Lerp or Slerp? thank you for the help :)

 public class TimeManipulation : MonoBehaviour {
 
     KeyCode timeManipualtionKey;
     public bool manipulatingTime;
     public bool manipulatingDown;
     public bool manipulatingUp;
     public float manipulationRate;
     public float timeManipulationDown = .5f;
     public float lerpSpeed = 10;
     public float durationOfManipulation = 2;
 
     float it = 1;
     float increment = .05f;
 
     void OnEnable()
     {
         timeManipualtionKey = this.GetComponent<Attributes> ().timeManipulation;
     }
 
     // Update is called once per frame
     void FixedUpdate () {
 
         if (Input.GetKeyDown (timeManipualtionKey)) {
             manipulatingTime = true;
             manipulatingDown = true;
         }
 
         if (manipulatingTime) {
             if (manipulatingDown) {
                 if (it >= .5f) {
                     print ("manipulating Down");
                     it -= increment;
                     Time.timeScale = it;
                     Time.fixedDeltaTime = 0.02f* Time.timeScale;
                 } else {
                     print ("finished manipulation Down");
                     manipulatingDown = false;
                     StartCoroutine (TimeInTheZone ());
                 }
             }
 
             if (manipulatingUp) {
 
                 if (it <= 1) {
                     print ("starting manipulating up");
                     it += increment;
                     Time.timeScale = it;
                     Time.fixedDeltaTime = 0.02f * Time.timeScale;
 
                 } else {
                     print ("manipulation ended");
                     manipulatingUp = false;
                     manipulatingTime = false;
                 }
             }
         }
     }
 
     IEnumerator TimeInTheZone()
     {
         print ("starting wait");
         yield return new WaitForSeconds (1);
         print ("wait ended");
         manipulatingUp = true;
         yield return null;
 
     }
 }