There is no central registry for births in France tho what happens is that - usually/frequently - information about marriages and deaths, divorces etc are annotated on local birth records.
Do you know whether
GERSEY is a commune with a consiel in its own right? If it is, you can ask the Mairie (Town
Hall) for an extract from their Etats-Civil for the birth.
If it's not a commune in its own right, you need to identify which 'local authority' it fall under and ask them.
But, be aware the Mairie is not bound to send you a copy, if they do, it will be a kindness on their behalf.
Alternatively, you can approach the Archive Departementale for
Eure and ask them as they are the repository for records in their Departemente. But, same thing applies, they are not bound to send you the information and they may refer you to a local genealogist/researcher/genealogical group, which you mau have to pay to get the information for you.
Regards
Tony
Fuller24220 Berbiguieres
France