Interpolate problem? Jump isn't smooth...

Hi, I have got a problem with jump... It's not smooth as I want it.. and I haven't got the idea how to fix it. Here is a video with my problem and my code. https://www.youtube.com/watch?v=Im1Vfr7TIwI&feature=youtu.be

public class Viva_Movement_Rigidbody : MonoBehaviour {

 [Header("Movement Variables")]
 public float moveSpeed = 5.0f;
 [Range(0.0f, 10.0f)]
 public float jumpSpeed;
 public float rotateSpeed = 10.0f;
 public bool isGrounded = false;

 [Header("Acceleration&Decceleration")]
 public float accSpeed = 2.0f;
 public float deccSpeed = 0.5f;
 public float airDeccSpeed = 0.2f;
 
 [Header("Other Variables")]
 public float height = 0.5f;

 public LayerMask ground;
 Rigidbody rb;

 float currSpeed = 0.0f;
 float deadzone = 0.19f;
 float angle;

 Vector2 input;

 Transform cam;
 Quaternion targetRotatiton;

 private void Start()
 {
     rb = GetComponent<Rigidbody>();
     cam = Camera.main.transform;
 }

 private void Update()
 {
     Debug.Log("currSpeed: " + currSpeed);
     GetInput();
     CalculateDirection();
     if (Mathf.Abs(input.x) < deadzone && Mathf.Abs(input.y) < deadzone)
     {
         Decceleration();
         Move();
     }else
     {
         Acceleration();
         Move();
         Rotate();
     }
 }

 private void FixedUpdate()
 {
     if (Input.GetButtonDown("XboxA") && isGrounded)
     {
         Jump();
     }
     GroundCheck();
 }

 void GetInput()
 {
     input = new Vector2(Input.GetAxisRaw("XboxHorizontal"), Input.GetAxisRaw("XboxVertical"));
     if (input.magnitude < deadzone)
         input = Vector2.zero;
     else
         input = input.normalized * ((input.magnitude - deadzone) / (1 - deadzone));
 }

 void CalculateDirection()
 {
     angle = Mathf.Atan2(input.x, input.y);
     angle = Mathf.Rad2Deg * angle;
     angle += cam.eulerAngles.y;
 }

 void Move()
 {
     transform.position += transform.forward * currSpeed * Time.deltaTime;
 }

 void Rotate()
 {
     targetRotatiton = Quaternion.Euler(0, angle, 0);
     transform.rotation = Quaternion.Slerp(transform.rotation, targetRotatiton, rotateSpeed * Time.fixedDeltaTime);
 }

 void Jump()
 {
     rb.velocity = new Vector3(rb.velocity.x, jumpSpeed * 40, rb.velocity.z) * Time.fixedDeltaTime;
     //rb.AddForce(Vector3.up * jumpSpeed * 40 * Time.deltaTime, ForceMode.Impulse);
 }

 void Acceleration()
 {
     currSpeed += accSpeed;
     if (currSpeed >= moveSpeed)
         currSpeed = moveSpeed;
 }

 void Decceleration()
 {
     if (isGrounded)
         currSpeed -= deccSpeed;
     else if (!isGrounded)
         currSpeed -= airDeccSpeed;

     if (currSpeed <= 0)
         currSpeed = 0;
 }

 void GroundCheck()
 {
     if (Physics.Raycast(transform.position, Vector3.down, height, ground))
         isGrounded = true;
     else
         isGrounded = false;
 }

}

Thanks for every idea how to fix it.