Firstly, git is complicated, but using github.com is a great way to understand its strengths and learn some of its best practices. This is the site I used during training, and it has good documentation on git workflow, tricks, etc. I recommend it as a way to go beyond the concepts that svn may have instilled, which is no longer applicable.
Regarding the organization of the repo between the teams, everything that matters most in the folder on any server equally applies to git, since git will essentially duplicate the entire folder that is the root of the repository at any time.
What can help is that different teams work in different industries and often cancel and often enter a stable central branch. I am currently using the main branch for production-ready code, the dev branch for potentially unstable code that deserves sharing and testing, but should not go live and local branches when I think of a new function that I can try.
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