Approch to merge a template with header and Items with Data for each entry

Question

I'm trying to learn Python and find a solution for my business.

I'm working on SAP and i need to merge data to fill a template.

Doing the merge based on Excel VBA, it's working but to fill a file with 10 K entries it's take a very long time.

My template is avaiable here https://docs.google.com/spreadsheets/d/1FXc-4zUYx0fjGRvPf0FgMjeTm9nXVfSt/edit?usp=sharing&ouid=113964169462465283497&rtpof=true&sd=true And a sample of data is here https://drive.google.com/file/d/105FP8ti0xKbXCFeA2o5HU7d2l3Qi-JqJ/view?usp=sharing

So I need to merge for each record from my data file into the Excel template where we have an header and 2 lines (it's a FI posting so I need to fill the debit and credit.

In VBA, I have proceed like that:

Fix the cell: Copy data from the template with function activecell.offset(x,y) ... From my Data file fill the different record based on technical name.

Now I'm trying the same in Python.

Using Pandas or openpyxyl I can open the file but I can't see how can I continue or proceed to find a way to merge header data (must be copy for eache posting I have to book) and data.

from tkinter import *
import pandas as pd
import datetime
from openpyxl import load_workbook
import numpy as np


def sap_line_item(ligne):
    ledger = ligne
    print(ligne)
    return


# Constante
c_dir = '/Users/sapfinance/PycharmProjects/SAP'


C_FILE_SEP = ';'
root = Tk()
root.withdraw()
# folder_selected = filedialog.askdirectory(initialdir=c_dir)
fiori_selected = filedialog.askopenfile(initialdir=c_dir)
data_selected = filedialog.askopenfile(initialdir=c_dir)

# read data
pd.options.display.float_format = '{:,.2f}'.format
fichier_cible = str(data_selected.name)
target_filename = fichier_cible + '_' + datetime.datetime.now().strftime("%Y%m%d-%H%M%S") + '.xlsx'
# target = pd.ExcelWriter(target_filename, engine='xlsxwriter')
df_full_data = pd.read_csv(data_selected.name, sep=C_FILE_SEP, encoding='unicode_escape', dtype='unicode')
nb_ligne_data = int(len(df_full_data))
print(nb_ligne_data)
#df_fiori = pd.read_excel(fiori_selected.name)
print(fiori_selected.name)
df_fiori = load_workbook(fiori_selected.name)
df_fiori_data = df_fiori.active

Any help to give some tick to approach and find a solution will be appreciate.

Have a great day

Philippe