Atlassian the company behind BitBucket, JIRA, SourceTree, etc. took some time and effort to write some tutorial about git.
Ranked in these QuestionsQuestion Ranking
Pro For beginners and experts
In the getting started section you can learn all about the basics of git. But they also tell you how to collaborate with the workflow "Git flow".
Open available on Atlassians website.
Pro Great structure
The tutorials are well structured and good to read.