Hi @staffanestberg
It sounds like you are wanting to create a select field and have the selected option determine the available choices for another select field. Is this correct?
Currently, this is not possible with ACF, but would be a great feature request.
I’ll add this to my list of features, but for now, you will need to write some custom jQuery to modify the choices available based on a select field.
Sorry I can’t provide an exact solution for this one.