Script controls 2 game objects not independently

I've recently started unity, so as a sort of exercise I wanted to make a remake of a Mario level. The part where i got stuck is when I made patrolling Goombas. It may be an inefficient and basic method, but essentially the idea is that I made them reverse direction when hitting another object. The problem is, that for some reason, when one hits a wall, both of them reverse direction. The script is, of course, applied to both.

   using UnityEngine;
     using System.Collections;
     
     public class GoombaMove : MonoBehaviour {
         public static float speed = -0.01f;
     
         // Update is called once per frame
         void Update () {
             this.transform.Translate(speed, 0, 0);
         
         }
         void OnTriggerEnter2D(Collider2D other)
         {
              speed *= -1;
         }
     }
     

I'm at a bit of a loss here...