Have you ever read any of the introductory material that the git project itself maintains for teaching how to use the tool?

- https://git-scm.com/docs/gittutorial

- https://git-scm.com/docs/giteveryday

- https://git-scm.com/docs/gitworkflows

- https://git-scm.com/docs/gitfaq

- https://git-scm.com/cheat-sheet

Or if you want to sit down and really learn the nuts and bolts

- https://git-scm.com/book/en/v2