How to change settings OnTrigger

I want to change the speed of my character to change when it collides with a box. A sort of speed-up boost, however I cannot get it to work whereby my code is most likely the problem.

function OnTriggerStay (other: Collider) {
ForwardSpeed = 20.0;
}

I’d also like to flip the camera and mirror the controls so that W is backward, S is forward, A is right and D is left. I hope someone can help out, I am new to Unity.

Thanks in advance

Finally I found out how to do this. Here’s my code.

FirstPersonController.cs:

using UnityEngine;
using System.Collections;

public class FirstPersonController : MonoBehaviour {

static public float movementSpeed = 5.0f;
public float mouseSensitivity = 2.0f;

float verticalRotation = 0;
public float upDownRange = 60.0f;

// Use this for initialization
void Start () {
	//Screen.lockCursor = true;
}

// Update is called once per frame
void Update () {
	//rotation

	float rotLeftRight = Input.GetAxis ("Mouse X") * mouseSensitivity;
	transform.Rotate(0, rotLeftRight, 0);

	verticalRotation -= Input.GetAxis ("Mouse Y") * mouseSensitivity;
	verticalRotation = Mathf.Clamp (verticalRotation, -upDownRange, upDownRange);
	Camera.main.transform.localRotation = Quaternion.Euler (verticalRotation, 0, 0);

	//movement
	float forwardSpeed = Input.GetAxis ("Vertical") * movementSpeed;
	float sideSpeed = Input.GetAxis ("Horizontal") * movementSpeed;

	Vector3 speed = new Vector3( sideSpeed, 0, forwardSpeed);

	speed = transform.rotation * speed;

	CharacterController cc = GetComponent<CharacterController>();

	cc.SimpleMove ( speed );

}

}

TriggerSpeed:

using UnityEngine;
using System.Collections;

public class TriggerSpeed : MonoBehaviour {

// Use this for initialization
void Start () {
	
}

// Update is called once per frame
void Update () {
	
}

void OnTriggerStay(Collider other) {
	FirstPersonController.movementSpeed = 20.0f;
}

}