I urgently need help with Typescript in react

Hello everyone, I am sitting now for five days in front of working code, but typescript stopps me with an error. I want to prefill input fields with data from my db. I am using redux-toolkit for getting this data and it works. I have all the data in my input fields. But typescript tells me:

The property X does not exist for type User.ts(2339)

How I can tell typescript that my code works? What it want from me? Can someone help me out? Thanks

Here the code in react:

interface Props{
    user:User,
    onEdit: (user: User) => void,
    setFormdata:React.Dispatch<React.SetStateAction<object>>
}
const UserDisplay:React.FC<Props> = () => {
    const dispatch = useAppDispatch();
    const selector = useAppSelector((state:RootState)=>state.user);
    const {user, isError, isLoading, message} = selector;
    const {id} = useParams();

    useEffect(()=>{
        if(isError){
            toast.error(message);
        }
        dispatch(getUser(id!));
        return ()=>{
            dispatch(reset())
        }
    }, [dispatch, isError, message, id]);
    const [formdata, setFormdata] = useState<{vorname:string, nachname:string, username:string, email:string, street:string, number:string,plz:string, city:string, isAdmin:boolean, createdAt:string}>({
        vorname:"",
        nachname:"",
        username:"",
        email:"",
        street:"",
        number:"",
        plz:"",
        city:"",
        isAdmin:false,
        createdAt:Date.toLocaleString(),
    })
    console.log(user);
    const {vorname, nachname, username, email, street, number, plz, city, isAdmin, createdAt} = formdata;

   
    useEffect(()=>{
        if(user){
            setFormdata({
                vorname:user.vorname, //Here all values are underlined with the error above
                nachname:user.nachname,
                username:user.username,
                email:user.email,
                street:user.street,
                number: user.number,
                plz:user.plz,
                city:user.city,
                isAdmin:user.isAdmin,
                createdAt:user.createdAt,
            })
        }
    }, [user])

Here the interfaces and initialState in redux-toolkit, perhaps it’s there, but I don’t think so:

export interface User{
  _id?:string,
  id?:string,
  vorname:string
  nachname:string
  username:string
  email:string
  street:string
  number:string
  plz:string
  city:string
  password:string
  isAdmin:boolean
  createdAt: Date
  accessToken: string;
}
interface InitialState{
    user:User[],
    isLoading:boolean,
    isSuccess:boolean,
    isError:boolean,
    message:string,
}
const initialState:InitialState ={
    user:[],
    isLoading:false,
    isSuccess:false,
    isError:false,
    message:"",
}

Best Roman