If you want to run your own git server on cloud9, I have to warn you that it's a very long process and very easy to screw up. If you still want want to set up your own server, take a look at this from the official site of Git: Git on the Server.
Instead, I would suggest you use GitHub (most popular but your code is public for the free account) or Bitbucket (...
That's not a problem at all. It's your project written by you. One of the main points of final projects is that you'll be able to use them to demonstrate your skills, which means you'll likely be including the project on your resume.
Hosting your project on GitHub is fine, and I'd actually encourage it. Learn to use version control and get involved in the ...
Have you done pset0 yet? Maybe you should start with that one.
In order to submit problem sets, you’ll need an account on GitHub, a popular service with which to store code and collaborate with others. If you don’t already have one, visit https://github.com/join and create an account (for free). ...
Better not use -a, as you might accidentally stage files you did not want to stage.
From git help commit:
Tell the command to automatically stage files that have been modified and deleted, but new files you have not told Git about are not affected.
Ctrl+C will cancel whatever program the terminal is running and send you back to your directory. Without knowing what command threw you into the loop, I can't help further, but this should at least kill the loop.
This may happen if your submission doesn't have the correct 'slug' (ie, you didn't use the exact submit50 command given in the spec)
In this case, does your submission Problem title say
If not, resubmit it with that submit50 cs50/2019/x/whodunit