Press Key for higher TimeScale and WaitForSeconds for lower TimeScale

Hey im new in things like Scripting and i need Help.Ahm i think this is false i want to press left ctrl then should my player run and if i wait 8 secs he should be again normaly walking.

Heres my Noob Script :D

function Update () {

if (Input.GetKeyDown("left ctrl")) {

Time.timeScale = 3.0; } if (Time.timeScale = 3.0) {

yield WaitForSeconds (8);

Time.timeScale = 1.0; } }

Hope you can help

Greetings