Help me understand the git workflow

So I currently work on a site for a small to medium sized company, where I'm the only Dev hired by them. We also work with another company that works on the site remotely for various purposes.

They just setup git and I'm not sure exactly how to proceed pushing code. Previously we just tested on local environments and pushed live. Now we have 3 branches / environments.

Dev, staging, and production

Do I need to push from local to Dev, then merge to staging, and merge again to production? Seems like a lot of work if the update is fairly small

Any help appreciated, thank you!