import pandas as pd
import numpy as np

epd = pd.read_csv("epd.csv", sep=";")

data = (
    pd.read_csv("details.csv", sep=";")
    [lambda x: (x['produkt_name'].str.contains('Cement', na=False)) & (x['umwelteinwirkung_id'] == '6a37f984-a4b3-458a-a20a-64418c145fa2')]
    .merge(epd)
)

rezept = (
    pd.DataFrame({
        'Artikelname': ['Zement 1', 'Zement 2', 'Zement 3'],
        'uuid': [
            '55af842c-7d33-4d0c-b33b-ac7564e573bf', 
            '49b9328a-3e77-4cea-98b8-5704a7b24883', 
            'a6376437-3772-4938-b7bb-d97b60628f11'
        ],
        'menge': [80, 90, 100]
    })  # <--- Hier muss die Klammer vom DataFrame zu!
    .merge(data)
    .assign(
        result = lambda x: x['wert'] * x['menge']
    )
    .groupby('umwelteinwirkung')['result']
    .sum()
    .reset_index()
)