Walking on a sphere, add collisions

Hi, i'm making a game where the character's walking around a sphere. I used this script for his movement :

  public class SphericController : MonoBehaviour
  {
      public SphericProjectile prefab;
  
      public float radius = 0.6f;
      public float translateSpeed = 180.0f;
      public float rotateSpeed = 360.0f;
      public float fireInterval = 0.05f;
 
      float angle = 0.0f;
      Vector3 direction = Vector3.one;
      Quaternion rotation = Quaternion.identity;
  
      void Fire()
      {
          var clone = (SphericProjectile)Instantiate(prefab);
          clone.transform.position = transform.position;
          clone.transform.rotation = transform.rotation;
          clone.transform.parent = transform.parent;
          clone.angle = angle;
          clone.rotation = rotation;
      }
  
      void Update()    
      {
         
         
          direction = new Vector3(Mathf.Sin(angle), Mathf.Cos(angle));
  
          // Fire bullet code
          if (Input.GetKeyDown(KeyCode.LeftControl))
              InvokeRepeating("Fire", float.Epsilon, fireInterval);
          if (Input.GetKeyUp(KeyCode.LeftControl))
              CancelInvoke("Fire");
         
          // Rotate with left/right arrows
          if (Input.GetKey(KeyCode.LeftArrow))  Rotate( rotateSpeed);
          if (Input.GetKey(KeyCode.RightArrow)) Rotate(-rotateSpeed);
  
          // Translate forward/backward with up/down arrows
          if (Input.GetKey(KeyCode.UpArrow))    Translate(0,  translateSpeed);
          if (Input.GetKey(KeyCode.DownArrow))  Translate(0, -translateSpeed);
  
          // Translate left/right with A/D. Bad keys but quick test.
          if (Input.GetKey(KeyCode.A))          Translate( translateSpeed, 0);
          if (Input.GetKey(KeyCode.D))          Translate(-translateSpeed, 0);
  
          UpdatePositionRotation();
      }
  
      void Rotate(float amount)
      {
          angle += amount * Mathf.Deg2Rad * Time.deltaTime;
      }
  
      void Translate(float x, float y)
      {
          var perpendicular = new Vector3(-direction.y, direction.x);
          var verticalRotation = Quaternion.AngleAxis(y * Time.deltaTime, perpendicular);
          var horizontalRotation = Quaternion.AngleAxis(x * Time.deltaTime, direction);
          rotation *= horizontalRotation * verticalRotation;
      }
  
      void UpdatePositionRotation()
      {
           transform.position = rotation * Vector3.forward * radius;
          transform.rotation = rotation * Quaternion.LookRotation(direction, Vector3.forward);
      }
  }

But i tried a lot of things to stop collision when the player collides a "wall". Nothing worked..

For instance i tried to add void OnCollisionEnter(Collision collision) { if(collision.collider.CompareTag("wall")) { collision.gameObject.GetComponent<Rigidbody>().velocity = Vector3.zero; print(collision); } } But it doesn't work. I think the problem is that the movement script uses transform.position method.

How can i solve my problem ? Thank you :)