sprint timer

okay my game is an rpgfps game. so I need help cleaning up my script for my controller. I plan to do this one question at a time so I won't be too vague. Firstly I'v now translated my script to c# and am getting a ton of compiler errors.

(And not to advertise so much but this is part of my open project : project VC anyone who wants to contribute can)

(119,37): error CS1503: Argument #1' cannot convert double' expression to type float' (119,37): error CS1502: The best overloaded method match forUnityEngine.WaitForSeconds.WaitForSeconds(float)' has some invalid arguments (121,1): error CS0103: The name `sprintTimer' does not exist in the current context

I picked these specifically because they seem they may be some of the main problem my largest problem is anything with yield because it is one of the main things I don't know much about in c# and i don't even know whats wrong with the sprint timer

i now my script is long put i can't even begin to figure out whats wrong with it

 void Update(){
  
 
 transform.Rotate(0,Input.GetAxis("Mouse X") * rotateSpeed * Time.deltaTime, 0);
 if(!swiming){
 //if (Input.GetButtonUp("Fire2")){
 if (Input.GetKeyUp("left shift")){
 sprintControl();
 }}
 //if (Input.GetButton("Fire2")){
     if(!swiming){
     if (Input.GetKey("left shift")){
         if(!isCoolingDown){
           
             if (currentSpeed <= maxSpeed){
                 currentSpeed++;
             } 
             else {
             if(Input.GetAxis("Vertical")){
                 animation.Play("walk");
                 sprintControl();
                 }
             }
         }
     }}
 }
 
 void FixedUpdate() {
    if (Input.GetKeyDown("q")){
  //moveDirection.y = jumpSpeed;
 animation.Play("roll");
 //Roll();
  
 }
     if(allowMove){
  
     if (grounded) {
         moveDirection = new Vector3(Input.GetAxis("Horizontal"), 0, Input.GetAxis("Vertical"));
         moveDirection = transform.TransformDirection(moveDirection);
        
         moveDirection *= currentSpeed;
 if(!swiming){
         if (Input.GetButton("Jump")) {
             moveDirection.y = jumpSpeed;
             //Roll();
         }
        if (Input.GetKeyDown("q")) {
        //animation.CrossFade("roll");
             moveDirection.y = jumpSpeed;
             Roll();
         }
         }
     }
     else if (climbing){
   
 
     moveDirection = new Vector3(Input.GetAxis("Horizontal"), Input.GetAxis("Vertical"),0);
         moveDirection = transform.TransformDirection(moveDirection);
        
         moveDirection *= currentSpeed;
 
     
 }
 }
 if(swiming){
 currentSpeed = walkSpeed;
 //isCoolingDown = true;
 if(Input.GetAxis("Vertical")){
 animation.Play("walk");
                 }
 }
 else{
 isCoolingDown = false;
 }
 moveDirection.y -= gravity * Time.deltaTime;
 CharacterController controller = GetComponent(CharacterController);//over load
 
 float flags = controller.Move(moveDirection * Time.deltaTime);
   
 grounded = (flags & CollisionFlags.CollidedBelow) != 0;
 controller.Move(moveDirection * Time.deltaTime);
 }
 
 //this will tell what to do when you've sprinted longer sprintStamina
 void sprintControl(){
 if(!swiming){
 sprintTimer += Time.deltaTime;//this is were the sprint timer is used
 if(sprintTimer > sprintStamina){
 StartCoroutine(dothis());
 }}}
 //this was newly added to make you slowdown and i believe this is where te overload error is 
 IEnumerator dothis (){
 currentSpeed = walkSpeed;
 isCoolingDown = true;
 yield return new WaitForSeconds(8.0);
 isCoolingDown = false;
 sprintTimer = 0.0;
 }
 
 //place my other junk here