How to GIT synchronize between origin and upstream branch

Git flow
This issue is because we want to update our local repository by merging the original sources. In this case, we use the “react-native-webrtc” package that forks from the repository.
In the first step, we create the new repository; in the example, I created the repo name with the prefix “custom” and then added the remote upstream, which refers to something that points to where it originated from.
git remote add upstream https://github.com/react-native-webrtc/react-native-webrtc.git
git fetch upstream
git checkout master
git merge upstream/master
git push origin

starting flow
Now that our branch has already updated from the upstream, let’s try to work on the basic workflow process. I start with the new branch and change the project name in package.json to a “custom-react-native-webrtc”. Following the image ref and cmd.

file has changed
git checkout -b "feature/test-merge"
git add .
git commit -m "change repo name"
git rebase origin/master feature/test-merge
git push origin feature/test-merge --force-with-lease
HINT: At the end of this step, we should create the PR to merge into the master branch.
Conclusion

Compare the upstream repository and our new repository with our synchronizing.
Repository
My repo example:https://github.com/andreaharris-go/custom-react-native-webrtc