Git command to commit a local replaced project to remote master

I am a total newbie on github. Now I am facing a problem which is:

  1. I uploaded my new project to github,with a same repo name as the project folder.

  2. Then I messed up the codes on local,want to recover the version I uploaded to github. Without knowing how to do so with github desktop client or git command, I deleted the folder from my local(laptop), then download the github copy and place it in the same directory.

  3. Now I have some update in my codes and I want to upload my newest version to github, commit to master branch, but I cant find the way to do so with desktop client or command. I tried to directly upload the whole folder to github website but cannot because the folder have exceed upload limit of website upload: more than 100 files inside.I also tried git command like:

    git push fypsubmission master fatal: 'fypsubmission' 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.

Please let me know what should I do, thanks