How to make a dash in c#? (Unity 2D)

Question

So, I am a really inexperienced scripter, so I would be so glad if you could help me. My friend made the movement system and he asked me to implement a dash, that's what he said to me: "I was thinking of just like grabbing a vector at a fixed distance and DOTWEENing to it". This is what I tried to do, unfortunately it doesn't work.

        ////GET THE INPUT AS A VECTOR/////
    Vector2 move = playerInput.Player.Movement.ReadValue<Vector2>();
    ////MOVE THE PLAYER/////
    playerRigidbody2D.MovePosition(transform.position + speed * Time.fixedDeltaTime * (Vector3)move);

        /////add a dash key here
        /////if dash and direction pressed
    if (Input.GetKeyDown(KeyCode.Space) && move != null)
    {
        playerRigidbody2D.MovePosition(transform.position += (Vector3)move * dashDistance);
    }