i want downloading now but never why
The device originally came with Microsoft Windows Phone 7.5 Mango. It is pretty old in terms of phones and sadly it cannot be updated to Windows Phone 8/8.1, and Skype for Windows Phone 7.8 is no longer supported. In fact, Windows Phone 7.x base ended
as of October 14, 2014.
Your best option is to get a new device.