Disable a Component with a script. Not working

@Nicolaiaiai

When you are trying to cache components as variables it's better to use the actual component class as the datatype rather than using the base class Component. This is because the component base class does not have a variable for enabling and disabling components.

So, if you want to get the FirstPersonController component, then specify the FirstPersonController as the datatype. For example, you would change your variables to the following:

 public class RespawnSystem : MonoBehaviour
  {
        FirstPersonController freezePlayer;
        MeleeSystem freezeAttacking;
        MeshRenderer weapon;
 
       // ...
 }

Also, when getting components, it's often better to use the generic way. So, all together, your class should now look like:

 public class RespawnSystem : MonoBehaviour
  {
      FirstPersonController freezePlayer;
      MeleeSystem freezeAttacking;
      MeshRenderer weapon;
      public Transform respawnLocation;
      public static bool playerIsDead = false;
  
      public Button buttonRespawn;
      public Button buttonMainMenu;
      public Button buttonQuitGame;
  
      void Start()
      {
          freezePlayer = GetComponent<FirstPersonController> ();
          freezeAttacking = GameObject.Find("FirstPersonCharacter").GetComponent<MeleeSystem> ();
          weapon = GameObject.Find("Axe").GetComponent<MeshRenderer> ();
      }
  
      void Update()
      {
          if (playerIsDead == true)
          {
              freezePlayer.enabled = false
              freezeAttacking.enabled = false
              weapon.enabled = false;
  
              buttonRespawn.gameObject.SetActive(true);
              buttonMainMenu.gameObject.SetActive(true);
              buttonQuitGame.gameObject.SetActive(true);
              Cursor.visible = true;
              Cursor.lockState = CursorLockMode.None;
          }
      }
 }

use this

 public GameObject otherobj;//your other object
     public string scr;// your secound script name
     void Start () {
     (otherobj. GetComponent(scr) as MonoBehaviour).enabled = false;
     }