Why the FormData is blank in react native

Question

1. Why when I do a console.log(), just after the last form.append("","") work well I see what I push in them, and than when I watch on the backend is blanked ?

2. Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client this error occured when I adding "Content-Type": "multipart/form-data" on the headers , do you know what happended ???

 const uri = pictureUri.uri;
 const uriParts = uri.split(".");
 const fileType = uriParts[1];

 const form = new FormData();

 form.append("categorie","someCategorieInthere");
 form.append("picture", {
   uri,
   name: `picture.${fileType}`,
   type: `image/${fileType}`,
 });

 const handlSubmit = async () => {
   try {
     await axios.put("blablbla_url",
       form,
       {
         headers: {
           Authorization: `Bearer ${token}`,
           Accept: "application/json",
           "Content-Type": "multipart/form-data",
         },
       }
     );
   } catch (error) {
     console.log({ message: error });
   }
 };