Hi,
I work in a product based firm in Bangalore with 5+ Years of Experience.
I have in-detail knowledge of GitHub, GitLab, Docker, BitBucket etc. for what you have mentioned in here.
I can teach you by example, how to setup a repository , to check-in the code, do a branching, create a Pull Request etc. etc.
If you want to learn it, it should take a minimum of 8 hours. 2 hours Each.
Let me know if you want me to go ahead and teach you over TeamViewer or however you want to connect.