How to concat files just downloaded with Selenium?

Question

Here's my code :

from selenium import webdriver
from selenium.webdriver.support.select import Select
from selenium.webdriver.support.ui import WebDriverWait     
from selenium.webdriver.common.by import By     
from selenium.webdriver.support import expected_conditions as EC
from selenium.webdriver.common.keys import Keys
import time
import shutil

PATH = "driver\chromedriver.exe"
driver = webdriver.Chrome(executable_path=PATH)
url = 'https://www.mergermarket.com/homepage'
driver.get(url)

deals = WebDriverWait(driver, 40).until(EC.element_to_be_clickable((By.XPATH, '//*[@id="header"]/div/div[2]/nav/ul/li[4]/a')))
urldeals = deals.get_attribute("href")
driver.get(urldeals)

start_date = datetime.date(2021, 2, 1)
start_date = datetime.datetime.strftime(start_date, '%d/%m/%Y')

middle_date = datetime.date(2021, 2,15)
middle_date = datetime.datetime.strftime(middle_date, '%d/%m/%Y')

delta = datetime.timedelta(days=15)

n = 1
m = 3

while n <= m:
      # Source path
      source = f"sourcepath/{n}new.xlsx"
 
      # Destination path
      destination = f"destinationpath/{n}new.xlsx"

      driver.get(urldeals)

      date = WebDriverWait(driver, 40).until(EC.element_to_be_clickable((By.XPATH, '//*[@id="date-picker_from"]')))
      date.click()
      date.send_keys(start_date) 
      time.sleep(1)

      date2 = WebDriverWait(driver, 40).until(EC.element_to_be_clickable((By.XPATH, '//*[@id="date-picker_to"]')))
      date2.click()
      date2.send_keys(Keys.CONTROL + "a")
      date2.send_keys(Keys.DELETE)
      date2.send_keys(middle_date)

      download = WebDriverWait(driver, 40).until(EC.element_to_be_clickable((By.XPATH, '//*[@id="__next"]/div/div/div[1]/div/div[2]/div[1]/div/div/div[2]/button[1]')))
      download.click()
      time.sleep(3)

      start_date = datetime.datetime.strptime(start_date, '%d/%m/%Y')
      middle_date = datetime.datetime.strptime(middle_date, '%d/%m/%Y')

      start_date = start_date + delta
      middle_date = middle_date + delta

      start_date = datetime.datetime.strftime(start_date, '%d/%m/%Y')
      middle_date = datetime.datetime.strftime(middle_date, '%d/%m/%Y')

      Initial_path = 'path/Downloads'
      filename = max([os.path.join(Initial_path, f) for f in os.listdir(Initial_path)], key=os.path.getctime)
      shutil.move(filename,os.path.join(Initial_path,f"{n}new.xlsx"))

      shutil.copy(source, destination)
      print("File copied successfully.")

      n = n+1
      time.sleep(1)

And here's my output, before the script was lauched the folder was empty :

How to concatenate those file into one ? They have the same variables so it must be not that hard but I cannot figure it out how to do that. It would be awesome if someone could give me some tips.