When using Pool.map from Python's built-in multiprocessing module, the program gradually slows down, why?

Question

Python

The same problem is described here: https://stackoverflow.com/questions/62869013/why-d...
Here is a piece of code:

from multiprocessing import Pool
Pool(processes=6).map(some_func, array)

After a few iterations, the program starts running in 5 threads, then 4, and so on. In the end, it seems to work even slower than without Pool.
I'm using this for a function with Selenium, could this be a problem?

Whole code:

# libraries
import os
from time import sleep
from bs4 import BeautifulSoup
from selenium import webdriver
from multiprocessing import Pool

# Необходимые переменные
url = "https://eldorado.ua/"
directory = os.path.dirname(os.path.realpath(__file__))
env_path = directory + "\chromedriver"
chromedriver_path = env_path + "\chromedriver.exe"

dict1 = {"Смартфоны и телефоны": "https://eldorado.ua/node/c1038944/",
         "Телевизоры и аудиотехника": "https://eldorado.ua/node/c1038957/",
         "Ноутбуки, ПК и Планшеты": "https://eldorado.ua/node/c1038958/",
         "Техника для кухни": "https://eldorado.ua/node/c1088594/",
         "Техника для дома": "https://eldorado.ua/node/c1088603/",
         "Игровая зона": "https://eldorado.ua/node/c1285101/",
         "Гаджеты и аксесуары": "https://eldorado.ua/node/c1215257/",
         "Посуда": "https://eldorado.ua/node/c1039055/",
         "Фото и видео": "https://eldorado.ua/node/c1038960/",
         "Красота и здоровье": "https://eldorado.ua/node/c1178596/",
         "Авто и инструменты": "https://eldorado.ua/node/c1284654/",
         "Спорт и туризм": "https://eldorado.ua/node/c1218544/",
         "Товары для дома и сада": "https://eldorado.ua/node/c1285161/",
         "Товары для детей": "https://eldorado.ua/node/c1085100/"}


def openChrome_headless(url1, name):
    options = webdriver.ChromeOptions()
    options.headless = True
    options.add_experimental_option("excludeSwitches", ['enable-automation'])
    options.add_argument(
        '--user-agent="Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.54 Safari/537.36"')
    driver = webdriver.Chrome(executable_path=chromedriver_path, options=options)
    driver.get(url=url1)
    sleep(1)
    try:
        with open(name + ".html", "w", encoding="utf-8") as file:
            file.write(driver.page_source)
    except Exception as ex:
        print(ex)
    finally:
        driver.close()
        driver.quit()


def processing_goods_pages(name):
    for n in os.listdir(f"brand_pages\\{name}"):
        with open(f"{directory}\\brand_pages\\{name}\\{n}", encoding="utf-8") as file:
            soup = BeautifulSoup(file.read(), "lxml")

        if not os.path.exists(f"{directory}\\goods_pages\\{name}\\{n[:-5]}"):
            if not os.path.exists(f"{directory}\\goods_pages\\{name}"):
                os.mkdir(f"{directory}\\goods_pages\\{name}")
            os.mkdir(f"{directory}\\goods_pages\\{name}\\{n[:-5]}")

        links = soup.find_all("header", class_="good-description")
        for li in links:
            ref = url + li.find('a').get('href')
            print(li.text)
            openChrome_headless(ref, f"{directory}\\goods_pages\\{name}\\{n[:-5]}\\{li.text}")


if __name__ == "__main__":
    ar2 = []
    for k, v in dict1.items():
        ar2.append(k)
    Pool(processes=6).map(processing_goods_pages, ar2)