does not appear to be a git repository

ubuntu@ip:~/African-Social-Food$ git remote add origin https://github.com/monajalal/African-Social-Food.git
fatal: remote origin already exists.
ubuntu@ip:~/African-Social-Food$ git pull
fatal: 'git@github.com/monajalal/African-Social-Food.git' does not appear to be a git repository
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.