How to start with this project? 3 tables multiple values

Difficult to say exactly but it seems like you need to create a composite key between RawMaterials and Recipes. So in PowerQuery, add a column to both like:

[MaterialID][Plant]

To create a unique key for each material by plant.

If I understand your scenario, I would do the following:

1. Add a column that merges Plant and Material in both your Raw Material and Recipes tables

2. Make a relationship between your two new columns (1:Many)

3. Use a measure like this - TotalCost = sumx(RawMaterials, RawMaterials[Preis]*Calculate(Sum(Recipes[Wert])))

I also assume you have a Date table that is filtering your Recipes table too.

If this works for you, please mark it as the solution.  Kudos are appreciated too.  Please let me know if not.

Regards,

Pat