Here's an ongoing list of nice resources (blog articles, tools, exercises, etc.) that may help in your journey with git.
The Git Parable http://bit.ly/1isB3K4
Pro Git -- official book http://git-scm.com/book/en/v2
Git Branching Exercises https://learngitbranching.js.org/
Visualizing Git http://git-school.github.io/visualizing-git/
Escaping a git mess http://justinhileman.info/article/git-pretty/git-pretty.png
Git / GitHub exercises https://lab.github.com/githubtraining/ramp-up-on-git-and-github
Tips for good code reviews https://mtlynch.io/code-review-love
Purging sensitive data https://docs.github.com/en/authentication/keeping-your-account-and-data-secure/removing-sensitive-data-from-a-repository
Cherry-picking vs merging (VERY technical) https://devblogs.microsoft.com/oldnewthing/20180312-00/?p=98215