Targetting Script Error Help

Hi Guys/Girls :) I need help with this Error: Assets/Scripts/Targetting.cs(77,11): error CS0029: Cannot implicitly convert type UnityEngine.GameObject' to UnityEngine.Transform'

Script:

 using UnityEngine;

using System.Collections; using System.Collections.Generic;

public class Targetting : MonoBehaviour { public List targets; public Transform selectedTarget;

 private Transform myTransform;
     
 void Start () {
     targets = new List<Transform>();
     selectedTarget = null;
     myTransform = transform;
     
     AddAllEnemies();
 }
 
 public void AddAllEnemies() {
     GameObject[] go = GameObject.FindGameObjectsWithTag("Enemy");
     
     foreach(GameObject enemy in go)
         AddTarget(enemy.transform);
 }
 
 public void AddTarget(Transform enemy) {
     targets.Add(enemy);
 }
 
 
 private void SortTargetsByDistance() {
     targets.Sort(delegate(Transform t1, Transform t2) {
             return Vector3.Distance(t1.position, myTransform.position).CompareTo(Vector3.Distance(t2.position, myTransform.position));
             });
 }
 
 private void TargetEnemy() {
     if(selectedTarget == null) {
         SortTargetsByDistance();
         selectedTarget = targets[0];
     }
     else {
         int index = targets.IndexOf(selectedTarget);
         
         if(index < targets.Count - 1) {
             index++;
         }
         else {
             index = 0;
         }
         DeselectTarget();
         selectedTarget = targets[index];
     }
     SelectTarget();
 }
 
 private void SelectTarget() {
     selectedTarget.renderer.material.color = Color.red;
     
     PlayerAttack pa = (PlayerAttack)GetComponent("PlayerAttack");
     
     pa.target = selectedTarget.gameObject;
 }
 
 private void DeselectTarget() {
     selectedTarget.renderer.material.color = Color.white;
     selectedTarget = null;
 }
 
 // Update is called once per frame

void Update () { if(Input.GetButtonDown("Fire1")) { Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
RaycastHit hit;
if(Physics.Raycast(ray, out hit, 100)) { if (hit.collider.gameObject.tag == "Enemy") { selectedTarget = hit.collider.gameObject; } } } } }

Any Ideas :)?