How to increase the speed of the character in OnTriggerEnter function?

Hi everyone,

I'm trying to make a game similar to something like Doodle Jump: The character move automatically up, with its speed that progressively decreases.

The issue that I encounter is with the stars, which are power-ups that boost speed for a small amount of time. I tried a lot of different things in the function OnTriggerEnter but it didn't work at all (except adding force to the rigidbody, but consequently I have the game over GUI that appears even if the character still moves, since it thinks that currentSpeed == minSpeed in the Update without taking into consideration the rigidbody.AddForce in the OnTriggerEnter).

There's my code:

 // Speed of the Player (left and right movements)
 var moveSpeed = 10f;  
 var movement;
     
 
 // Decrease-Increase speed (up)
 var maxSpeed = 30.0;
 var minSpeed = 0.0;
 var maxAcceleration = 1.0; // Controls the acceleration
 var maxAcceleration2 = 8.0; // Controls the acceleration
 var currentSpeed = 30.0;
 //var currentSpeed2 = 30.0;
 
         
 // GUI that appears when Game Over    
 var showGUI : boolean = false;
 
 var iconGO : Texture2D;
 var iconRetry : Texture2D;
 var iconBack : Texture2D;
 var positionGO :  Rect;
 var positionRetry :  Rect;
 var positionBack :  Rect;
             
                     
     
 function Update() 
 {  
     // gameplay Player (left and right)
     movement = Input.GetAxis("Horizontal") * moveSpeed;  
     movement *= Time.deltaTime;  
     transform.Translate(0.0f,0.0f, movement);
     
     
     // moving automatically up
     transform.Translate(Vector3.up * Time.deltaTime * currentSpeed);
     
     // decreasing speed
     if (currentSpeed > minSpeed)
     {
     currentSpeed -= maxAcceleration * Time.deltaTime;
     currentSpeed = Mathf.Clamp(currentSpeed, minSpeed, maxSpeed);
     }
     
     // when the character stops, GUI Game Over
     if (currentSpeed == minSpeed)
     {
     //Debug.Log ("YES"); //working (currentSpeed == 0.0)
     showGUI = true;
     }
     
 }
     
             
 function OnTriggerEnter(other: Collider)
 {
     if (other.tag == "Stars")
     {
         // Works but the GUI appears before the character stops (when it takes star(s)):
         //rigidbody.AddForce (0, 300, 0);
         
         //Debug.Log ("YES 02"); //working (collision)
         
         // one of the many tests that I tried:
         transform.Translate(Vector3.up * Time.deltaTime * maxSpeed);
         maxSpeed += maxAcceleration2 * Time.deltaTime;
         maxSpeed = Mathf.Clamp(maxSpeed, minSpeed, currentSpeed);
         
         // an other one that I tried:
         transform.Translate(Vector3.up * Time.deltaTime * currentSpeed2);
         currentSpeed2 += maxAcceleration2 * Time.deltaTime;
         currentSpeed2 = Mathf.Clamp(currentSpeed2, minSpeed, maxSpeed);
         
     }
 }
     
     
     
 function OnGUI()
 {
     if(showGUI)
          
     {
     
         if(GUI.Button(positionGO, iconGO, "label"))
         {
             // Image Game Over
         }
         
         else if(GUI.Button(positionRetry, iconRetry, "label"))
         {
             // Button that reloads the current scene
             Application.LoadLevel("RUNNER");
         }
             
         else if(GUI.Button(positionBack, iconBack, "label"))
         {
             // Button that allows to go back to the menu
             Application.LoadLevel("MENU");
         
         }
         
     }
 }

Maybe, to resolve it easily, is there a code that simply says "show me the GUI once my character stopped (so, not related to currentSpeed and minSpeed in the Update)" ?

Thanks in advance for all the help I can get !