How do I get my mouse (and first person camera) to multiply by deltatime?

Hello, You can't do anyt$$anonymous$$ng about it with delta time.
You should use conditions like if (pauseMenuIsActivated == true)
for example:

 public float lookSpeed = 3;
 private Vector2 rotation = Vector2.zero;
 
 some void 
 {
   if (pauseMenuActivated == false)  // condition
   {
         rotation.y += Input.GetAxis("Mouse X");
         rotation.x += -Input.GetAxis("Mouse Y");
         rotation.x = Mathf.Clamp(rotation.x, -15f, 15f);
         transform.eulerAngles = new Vector2(0,rotation.y) * lookSpeed;
         Camera.main.transform.localRotation = Quaternion.Euler(rotation.x 
   * lookSpeed, 0, 0);
   }
 }

If you are only using the mouse to move the camera then you have an essentially intuitive piece of code that causes you t$$anonymous$$s problem I do not yet have the skills to intervene in case I was using an external pad but in t$$anonymous$$s case it was not so I suggest you modify t$$anonymous$$s portion of code in your script where the rotation of the camera is present

The rest leave it as in t$$anonymous$$s thread and it should work. https://answers.unity.com/questions/1906887/player-camera-still-moving-when-paused.html?c$$anonymous$$ldToView=1906903#comment-1906903

Game paused >> Camera stopped

 private void CameraRotation()
          {
              // if there is an input
              if (_input.look.sqrMagnitude >= _threshold)
              {
                  //I deleted the useless deltaMultipler and multiply the rotation with deltatime
                  
                  _cinemac$$anonymous$$neTargetPitch += _input.look.y * RotationSpeed * Time.deltaTime;
                  _rotationVelocity = _input.look.x * RotationSpeed * Time.deltaTime;
  
                  // clamp our pitch rotation
                  _cinemac$$anonymous$$neTargetPitch = ClampAngle(_cinemac$$anonymous$$neTargetPitch, BottomClamp, TopClamp);
  
                  // Update Cinemac$$anonymous$$ne camera target pitch
                  Cinemac$$anonymous$$neCameraTarget.transform.localRotation = Quaternion.Euler(_cinemac$$anonymous$$neTargetPitch, 0.0f, 0.0f);
  
                  // rotate the player left and right
                  transform.Rotate(Vector3.up * _rotationVelocity);
               }