Github：non-fast-forwardエラーの対処法

git pushを行いたいと思っています。

ですが、現状、git push時に以下のエラーが出ます。

vagrant@ubuntu-xenial:~/workspace/twitter$ git push git@github.com: name/Twitter.git master
To git@github.com:Momoko-Takita/Twitter.git
 ! [rejected]        master -> master (non-fast-forward)
error: failed to push some refs to 'git@github.com: name /Twitter.git'
hint: Updates were rejected because the tip of your current branch is behind
hint: its remote counterpart. Integrate the remote changes (e.g.
hint: 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.

やったこと

・git pullが必要だと考えたのでgit pullしたら以下のエラーが出ました

agrant@ubuntu-xenial:~/workspace/twitter$ git pull git@github.com: name /Twitter.git master
warning: no common commits
remote: Enumerating objects: 96, done.
remote: Counting objects: 100% (96/96), done.
remote: Compressing objects: 100% (81/81), done.
remote: Total 96 (delta 2), reused 96 (delta 2), pack-reused 0
Unpacking objects: 100% (96/96), done.
From github.com: name /Twitter
 * branch            master     -> FETCH_HEAD
Auto-merging package.json
CONFLICT (add/add): Merge conflict in package.json
Auto-merging db/schema.rb
CONFLICT (add/add): Merge conflict in db/schema.rb
Auto-merging config/secrets.yml
CONFLICT (add/add): Merge conflict in config/secrets.yml
Auto-merging config/routes.rb
CONFLICT (add/add): Merge conflict in config/routes.rb
Auto-merging config/environments/production.rb
CONFLICT (add/add): Merge conflict in config/environments/production.rb
Auto-merging config/database.yml
CONFLICT (add/add): Merge conflict in config/database.yml
Auto-merging config/cable.yml
CONFLICT (add/add): Merge conflict in config/cable.yml
Auto-merging config/application.rb
CONFLICT (add/add): Merge conflict in config/application.rb
Auto-merging bin/rake
CONFLICT (add/add): Merge conflict in bin/rake
Auto-merging bin/rails
CONFLICT (add/add): Merge conflict in bin/rails
Auto-merging app/views/layouts/application.html.erb
CONFLICT (add/add): Merge conflict in app/views/layouts/application.html.erb
Auto-merging app/assets/javascripts/application.js
CONFLICT (add/add): Merge conflict in app/assets/javascripts/application.js
Auto-merging README.md
CONFLICT (add/add): Merge conflict in README.md
Auto-merging Gemfile.lock
CONFLICT (add/add): Merge conflict in Gemfile.lock
Auto-merging Gemfile
CONFLICT (add/add): Merge conflict in Gemfile
Auto-merging .gitignore
CONFLICT (add/add): Merge conflict in .gitignore
Automatic merge failed; fix conflicts and then commit the result.

・このエラーが出たのでmergeする必要があると考えたので

vagrant@ubuntu-xenial:~/workspace/twitter$ git push git@github.com:name/Twitter.git
fatal: The current branch master has no upstream branch.
To push the current branch and set the remote as upstream, use

    git push --set-upstream git@github.com:name/Twitter.git master

あとはエラーに対処していっただけです、、、

vagrant@ubuntu-xenial:~/workspace/twitter$ git push git@github.com:name/Twitter.gitmaster
fatal: The current branch master has no upstream branch.
To push the current branch and set the remote as upstream, use

    git push --set-upstream git@github.com:name/Twitter.gitmaster master

vagrant@ubuntu-xenial:~/workspace/twitter$ git push --set-upstream git@github.com:name/Twitter.gitmaster master
ERROR: Repository not found.
fatal: Could not read from remote repository.

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

ブランチはMasterブランチしかありません。
今はgit pull を行っても以下のエラーが起きるようになりました。

fatal: This operation must be run in a work tree

お尋ねしたいこと

git push ができない原因はmergeができていないことが原因だと考えてるのですが、
なかなかマージがうまくいきません。
マージの仕方が悪いのでしょうか？

また、うまくいっていない理由は他にあるのでしょうか？

よろしくお願いいたします。