Connection BT Speed on Android

Hi to all, i've an PCL App in Xamarin.Forms that must to print a label. The code for printing is the same on Ios and Android but on Android the bold instruction takes more than 25 seconds in Android while on Ios the answer comes in just under 10 seconds :

        public async void Print()

        {

            string zpl = myZpl;

            string address = PrinterHelper.GetSerialNumber();

            bool statusForPrintingOK = true;

            try

            {

                IConnection connectionPrint = null;

                connectionPrint = ConnectionBuilder.Current.Build(address);

                try

                {

                   connectionPrint.Open();

                    IZebraPrinter printer = ZebraPrinterFactory.Current.GetInstance(PrinterLanguage.ZPL, connectionPrint);

                    IPrinterStatus status = printer.CurrentStatus;

                    if (status != null)

                    {

                        if (status.IsPaperOut)

                        {

                            _messagePaper = "\n" + Helper.PrinterPaperFinished;

                            statusForPrintingOK = false;

                        }

                        if (status.IsHeadOpen)

                        {

                            _messageHeadOpen = "\n" + Helper.PrinterPaparSlotOpen;

                            statusForPrintingOK = false;

                        }

                        if (statusForPrintingOK)

                        {

                            bool languageSetting = SetPrintLanguage(connectionPrint, lenghtLabelToPrint);

                            connectionPrint.Write(Encoding.UTF8.GetBytes(zpl));

                        }

                        else

                        {

                            MessagingCenter.Send<ReprintAndVoid, string>(this, "RePrintFailed", "ReprintFail");

                            connectionPrint.Close();

                        }

                    }

                    else

                    {

                        ...

                    }

                }

                catch (Exception ex)

                {

                   .....

                }

            }

            catch (Exception e)

            {

                         .....

            }

            finally

            {

                    ...

            }

        }

I use Zebra Imz320 with last firmware. I wrong something? The device is "Samsung Galaxy Tab A6 (SM-T585)" with Android 7.0

Thanks in advance.

Nicola