How to increase data transfer speed over BLE?

Question

Bluetooth

Good day. I have a firmware hex file about 60kb in size, which I feed to my device via BLE. In fact, the file was completely transferred in 5 minutes, which is a lot. I act in the following way. Transmission of each specific message

public class BluetoothConnector 
{
///…
        public GattCharacteristic WriteCaracteristic { get; private set; }
///...

    public async void SendMessageAsync(byte[] byteMessage)
    {
        var characteristic = WriteCaracteristic;

        if (characteristic == null)
        {
            return;
        }

        var writer = new DataWriter();
        writer.WriteBytes(byteMessage);
        var result = await characteristic.WriteValueAsync(writer.DetachBuffer());
    }
///...
}

Firmware Transfer

public class MessageManager
{
    ///...
    public BluetoothConnector Connector { get; set; }
    ///...
    public void StartProgramming(List<byte[]> programm)
    {
        foreach (var message in programm)
        {
            Connector.SendMessageAsync(message);
        }         
    }
///...
}

The List program has a length of about 1000. And in fact, the foreach loop completes in a couple of seconds, but the data takes a very long time to reach the device. I use the standard uwp library to work with BLE. I did not find anything about adjusting the data transfer rate. Can something be done about it?