something is wrong with terminal. Plz have a look at my code

(kali㉿kali)-[~]
└─$ sudo add-apt-repository ppa:myunity/ppa                                                            100 ⨯
sudo apt-get update
sudo apt-get install myunity
sudo: add-apt-repository: command not found
Ign:1 http://http.kali.org/kali kali-rolling InRelease
Ign:1 http://http.kali.org/kali kali-rolling InRelease
Ign:1 http://http.kali.org/kali kali-rolling InRelease
Err:1 http://http.kali.org/kali kali-rolling InRelease
  Temporary failure resolving 'http.kali.org'
Reading package lists... Done
W: Failed to fetch http://http.kali.org/kali/dists/kali-rolling/InRelease  Temporary failure resolving 'http.kali.org'
W: Some index files failed to download. They have been ignored, or old ones used instead.
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
E: Unable to locate package myunity