I just realized that I messed up the formatting. Actually what I'm looking for should be like this:

{
1971:{"nickname":"Robby1","age":28,"age_p":42,"city":"Dresden","plz":"","wio_plz":"2,4,5","gender":"m"},
1972:{"nickname":"Robby2","age":29,"age_p":43,"city":"Dresden2","plz":"","wio_plz":"4,5","gender":"f"},
1973:{"nickname":"Robby3","age":30,"age_p":44,"city":"Dresden3","plz":"","wio_plz":"5","gender":"m"}
}