B4R Question Convert to string

"Cannot modify Global (non-primitive) Variable

Private ser As B4RSerializator
    Private BE(20) As Object
    Dim humiditytosend(),temperaturetosend() As Byte
    Private bc As ByteConverter
Private Sub Arduino_Received_Data(buffer() As Byte)
ser.ConvertBytesToArray(buffer,BE)
Log("Humid from Ardiono :",BE(0))
Log("Temp from Arduino :",BE(1))
'bc.ArrayCopy(BE(0),humiditytosend)
GlobalStore.Put(0,BE(0))   'For Humid
Log("Humid is:",GlobalStore.Slot0)

Dim s As String = bc.StringFromBytes(GlobalStore.Slot0)

#if C
#include <ESP8266WiFi.h>
#include <WiFiClient.h>
#include <ESP8266WebServer.h>
#include <ESP8266HTTPClient.h>
void setup(B4R::Object* o){
const char *host = "http://mypage.com";
}
void read (B4R::Object* o) {
    HTTPClient http;    //Declare object of class HTTPClient
    String getData, Link ;

  //GET Data
  getData = "?temperature=" + temperature + "&humidity=" + humidity ;
  Link = "http://mypage.com/addTemperature.php" + getData;
  http.begin(Link);     //Specify request destination
 
  int httpCode = http.GET();            //Send the request
  String payload = http.getString();    //Get the response payload

  Serial.println(httpCode);   //Print HTTP return code
  Serial.println(payload);    //Print request response payload

  http.end();  //Close connection
}
#End if

#if C
String temperature, humidity;  <--- Can assign any value from GlobalStore
#End if