Everyone. I'm so glad to post this question here.
I've been googling so far and I found some answer about this permission issue but they didn't help me. After generating new SSH keys and adding to GitHub my own Account, this problem is being issued continuously. I use Ubuntu 16.04. If you have correct to this question, please let me know. I'll be happy by your any idea, so please recommend any solution.
Thanks for your time. Falcon.Guru