There are a number of resources to learn Git available on the internet. Feel free to use any of them. However, if you are looking for suggestions, you can go for the following -
Get an overview of what VCS is - https://guides.github.com/introduction/git-handbook/
It takes a lot of time to learn git branching, but this tool is very useful - https://learngitbranching.js.org/ Solve the exercises there honestly :-)
Reference sheet with git commands - https://services.github.com/on-demand/downloads/github-git-cheat-sheet.pdf
Note that git is a very large software with lots of features, and we DON'T recommend that you learn all of these right now. Just learn the basics. It'll be better if you learn the more advanced features as and when required. Google is your friend :-)