How can I make my turret also rotate on the X-axis?

I am following a part of a tutorial from Brackeys on making a Tower-defense game, where they code-in the turret AI for engaging targets, but I'm using it in my own game, to create hostile turrets, which target the player. I thought adding a rotation.x instead of a 0 on partToRotate.rotation = Quaternion.Euler(rotation.x, rotation.y, 0f); would fix it, but it still only rotates on Y only. I have looked at it to search for any syntax mistakes, that I'd be able to fix, but it all seems fine to me, so why doesen't it rotate on the Y axis as well?

If someone gives me an answer, can you also just quickly explain why this will not work? I am checking the documentation and am a bit stumped, atough I'm a complete newbie.

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class SentryAI : MonoBehaviour
 {
 
     public Transform targetingPlayer;
     public float range = 15f;
 
     public Transform partToRotate;
     public float sentrySpeed = 5f;
 
     public string playerTag = "Player";
     void Start()
     {
         InvokeRepeating("UpdateTarget", 0f, 2f);
     }
 
     void UpdateTarget()
     {
         // Only some variable names were changed, since I want the turrets to target the player
 
         GameObject[] enemies = GameObject.FindGameObjectsWithTag(playerTag);
         float shortestDistance = Mathf.Infinity;
         GameObject nearestEnemy = null;
 
         foreach (GameObject enemy in enemies)
         {
             float distanceToEnemy = Vector3.Distance(transform.position, enemy.transform.position);
             if (distanceToEnemy < shortestDistance)
             {
                 shortestDistance = distanceToEnemy;
                 nearestEnemy = enemy;
             }
         }
         // Target nearest enemy - may be unnecessary
         if (nearestEnemy != null && shortestDistance <= range)
         {
             targetingPlayer = nearestEnemy.transform;
         }
         else
         {
             targetingPlayer  = null;
         }
     }
 
     void Update()
     {
         if (targetingPlayer == null)
             return;
         // This is the lock-on
 
         Vector3 dir = targetingPlayer.position - transform.position;
         Quaternion lookRotation = Quaternion.LookRotation(dir);
         Vector3 rotation = Quaternion.Lerp(partToRotate.rotation, lookRotation, Time.deltaTime * sentrySpeed).eulerAngles;
         partToRotate.rotation = Quaternion.Euler(rotation.x, rotation.y, 0f);
 
     }
 
 
 
     private void OnDrawGizmosSelected()
     {
         Gizmos.DrawWireSphere(transform.position, range);  
     }
 }
 

This is the code.

Also additionaly - will partToRotate.x = Mathf.Clamp(turretTurn.x, minRotationX, maxRotationX); work with the turret, if I want to clamp the angles on which it is able to rotate, like in my other script for turning the player's turret?

Thanks a lot for any replies. The few answers on here that I got on my last post helped me learn a lot <3 I have checked multiple forums and videos for answers, but I cannot figure it out in time for a gamejam.