Problem whit Opening and closing Door

Hi to all!
I did a animation for opening a door, i did a script that if i press B the door opens, for closing i put -1f at the animation, but not very good… the closure is very fast… and after on time that I press B and A, the animation doesn’t reproduce more… please help me i’m going crazy …

void Update () {

    if (Input.GetKeyDown (KeyCode.B)) { 
     animation.Play("New Animation");
    }
    
    if (Input.GetKeyDown (KeyCode.A)) { 
    animation["New Animation"].time = animation["New

Animation"].length;
animation[“New Animation”].speed = -1f;
animation.Play();

   }
 } }

Try:

    animation["New Animation"].speed = -0.1f;

This will play it backward at 1/10th speed.