Hello fellas, 
Well as you may see on the topic name I'm getting this error from the hurtworld SDK, 
now the following thing is I don't know what the issue is, 
Because I have rebooted my pc already installed the unity software as well,
And still getting this error, 
So if someone has a solution  for me please let me know 
https://www.upload.ee/image/8837393/bug....png

SDK is not a program, its just a game files which you use to make your Mods. So to "open" SDK you must install Unity 5.6.6, gets into steamapps/common/hurtworld SDK and extract the HurtworldModTemplate zip file, then open Unity and open the folders from HurtworldModTemplate as project.