Hi Juancar,
Are there any more images of this bird? While it may well be a Herring Gull, as Jean says, I am finding it difficult to conclusively exclude a darker lusitanius Yellow-legged Gull. I have never (knowingly) seen this taxon, not having visited its geographical range, but some birds can be quite well-marked below. Something about the head and bill on this bird look, if not wrong for Herring Gull, interesting enough to make me wonder.
Regards,
Harry