Neither CursorLockMode.Confined or SetResolution work

I am making a strategy game and I want my camera to scroll when I position my mouse on the edge of the screen. But it's annoying when the mouse can move outside the game window, I have to be pixel perfect for my camera to move.

So I wanted to confine my mouse to game window, but it didn't work. Then I tried making the game window fullscreen, that didn't work either.

Here's the code:

     private float _scrollSpeed;
 
     private void Start()
     {
         _scrollSpeed = 10.5f;
         // Doesn't work. 
         Screen.SetResolution(1920, 1080, true);
 
         
     }
 
     private void Update()
     {
         ScrollBehaviour();
         if (Input.GetKey(KeyCode.Space))
             Cursor.lockState = CursorLockMode.None;
     }
 
     private void ScrollBehaviour()
     {
         Vector3 direction;
         if (Input.mousePosition.x == 0) // I kaire
         {
             direction = new Vector3(-1, 0, 0) * _scrollSpeed * Time.deltaTime;
             gameObject.transform.parent.Translate(direction, Space.Self);
         }
         if (Input.mousePosition.y == 0) // I apacia
         {
             direction = new Vector3(0, 0, -1) * _scrollSpeed * Time.deltaTime;
             gameObject.transform.parent.Translate(direction, Space.Self);
         }
         if (Input.mousePosition.x == Screen.width-1) // I desine
         {
             direction = new Vector3(1, 0, 0) * _scrollSpeed * Time.deltaTime;
             gameObject.transform.parent.Translate(direction, Space.Self);
         }
         if (Input.mousePosition.y == Screen.height) // I virsu
         {
             direction = new Vector3(0, 0, 1) * _scrollSpeed * Time.deltaTime;
             gameObject.transform.parent.Translate(direction, Space.Self);
         }
     }
 
     void OnGUI()
     {
         // This works. 
         if (GUI.Button(new Rect(0, 0, 100, 50), "Lock Cursor"))
         {
             Cursor.lockState = CursorLockMode.Locked;
         }
 
         // But this doesn't work. 
         if (GUI.Button(new Rect(125, 0, 100, 50), "Confine Cursor"))
         {
             Cursor.lockState = CursorLockMode.Confined;
         }
     }

I am not sure if Screen.SetResolution is the right fucntion for making game screen fullscreen, but it doesn't do anything. All help is appreciated.