ᐅ How to Remove Formwork Oil Stains from a Ground Floor Ceiling?

Hello,

we are currently having our single-family house built by a developer. We will only be doing the painting and flooring ourselves. We have now noticed that there are several shuttering oil stains on the ground floor ceiling. A coat of paint does not hold despite priming. We had actually expected the developer to fix the damage. However, they are not doing so. Therefore, our question is: what options are there to remove these stains so that we can paint the ceiling?