Ciao @Nicoleta47 ,
the “Firma Elettronica Avanzata” is an authentication of your identity certified by an Italian provider (like Aruba, Poste, Telecom ecc) but you need to have an Italian ID. With a residency in Italy or at least if you were born in Italy and you have an Italian tax number you can apply for an Italian ID.
Types of “Firma elettronica avanzata” (FEA) are SPID (sistema pubblico di identità digitale), CIE (Carta identità elettronica italiana), CNS (Carta nazionale dei servizi), all related to your Italian ID.
As I answered you in another post, as an EU citizen (but UK is not more EU) you can apply for a FEQ in administrations enabled with the EIDAS.
The identification of this signatory is carried out by a certifier recognized by AglD (Agenzia per l’Italia digitale) and this makes the signature valid in any context, like with the FEA. The obligation to accept this signature is sanctioned at the European level from the regulation ElDAS.
Once you have entered the public administration (municipalities, regional website, police department to register your property for tourist rental) in Italy with you FEA (or FEQ) you are requested to sign several documents on their websites with your “Firma digitale remota” (this means it is a Firma Elettronica Semplice FES) which you can obtain for a fee by a provider like Aruba ecc.