How can i get the windows phone app because it is not available in my country and i really need it.

Windows Phone app is indeed currently not available in many countries.

The app has never worked well.

You have to wait until it will be available again.

When you have already install an older version there is a third party fix for it:

http://lowendmac.com/2015/el-capitan-windows-phone-app-fix/

https://tubeapps.net/wp8/

But there is another way to sync the Windows phone to a Mac:

http://www.imore.com/mac-switcher-can-my-windows-phone-work-my-mac