Merge two Git repositories?

Question

git

The bottom line is this:
1) I have a project on GitHub, I work with the project at home, I commit changes to GitHub
2) At work, all the ports on which git works are closed, so I download the ZIP from GitHub, deploy it to the local Git repository. When downloading a ZIP from GitHub, only files without GitHub repository data are downloaded, i.e. at work I get a separate repository.
3) I make some changes at work, commit to the local repository, copy the repository to a USB flash drive, bring it home
QUESTION: how can I now merge the repository from work with the home repository (which is connected to GitHub). Or maybe there is some easier option, how can I synchronize work between home, work and GitHub?

Answer 1

You can also work with github via http(s). These ports are usually open.
Example:
But if you go through a proxy at work, then you will also have to register it.

Answer 2

And on a flash drive, what prevents you from keeping a local repository whose remote origin is set to github?