I would take the covers off the cushions - usually they have a zipper.
The insides of the cushions probably would not make it through a washer.
If they don't have a zipper, your best bet is probably to buy a spray-on carpet & upholstery cleaner like Resolve or Spot Shot - I don't know what they have in France - spray on, let dry, vacuum off.
Dry cleaning cushions is horribly expensive here...