Variables in the prefab cannot be set.

I am making a multiplayer game and I am facing a problem. in the prefab, i cannot set object / UI variables, like, completely. And there are a lot of variables and I cannot write for each search by tag or something else. Can anyone tell me how to solve this or an alternative way of the player appearing on the scene without a prefab?

i kinda got the solution, but just to check: is this ok?

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
using Mirror;

public class StatsBank : MonoBehaviour
    public HpStuff HpS;
    public Cursor_building curs;
    void Start()
        GameObject gpl = GameObject.FindGameObjectWithTag("StatsBank");
        HpStuff hpl = gpl.GetComponent<HpStuff>();
        HpS.HpBar = hpl.HpBar;
        HpS.MetallBar = hpl.MetallBar;
        HpS.Handle = hpl.Handle;
        HpS.InventStuff = hpl.InventStuff;