Trying to use Git but not so clear on how to learn

I have been trying to learn Git + GitHub to start teaching at the school. Without understanding the correct use, and potential problems that we could face when using this technology I am not so confident to do it.
Yet, I have finished the Udacity course, a course with a campus expert, and again and again the problem is the nature of the examples. At some point, they lose attention to the learning curve and start using complex examples that does not make any sense at all, thus the problem is not about using GitHub but to figure out where an error o diff is present.

So I am here, to try to find the right approch to learn and then to teach GitHub.