SpawnManager_2.cs

using System;
using UnityEngine;
using Random = UnityEngine.Random;

public class SpawnManager_2 : MonoBehaviour
{
    public GameObject[] animalPrefabs;
    private float startTime = 2;
    
    void SpawnRandomAnimals()
    {
        int animalIndex = UnityEngine.Random.Range(0, animalPrefabs.Length);
        int positionX = UnityEngine.Random.Range(-20, 20);

        Instantiate(animalPrefabs[animalIndex], new Vector3(positionX, 0, 20),
            animalPrefabs[animalIndex].transform.rotation);
    }

    void SpawnAnimalsFromSide()
    {
        int animalIndex = UnityEngine.Random.Range(0, animalPrefabs.Length);
        
        float randomZ = UnityEngine.Random.Range(2, 15);
        Vector3 spawnPos = new Vector3(-25.0f, 0, randomZ);
        
        Quaternion spawnRot = Quaternion.Euler(0, 90, 0);
        
        Instantiate(animalPrefabs[animalIndex], spawnPos, spawnRot);
    }
    
    void Start()
    {
        InvokeRepeating("SpawnRandomAnimals", startTime, Random.Range(2,6));
        InvokeRepeating("SpawnAnimalsFromSide", startTime+2, Random.Range(3,7));
    }
void Update()
    {
        
    }
}