How do you remove carpet glue stain on marble floor?

Answer Difficult to judge from here. If the adhesive was brown it may have penetrated the marble you need to grind the marble and use hydrogen peroxide. A treatment only for VERY experienced professionals.

If the marble has been wet for a few days, there is probably also some rust the stone. Marble may contain pyrite (fools gold, iron ore).

Suggest you ask a marble restorer to have a look.

Check the yellow pages "granite" or "marble" or "natural stone"