There is no direct way to replace the master branch of your git project with the working branch (or any other branch), but with the ‘ours‘ strategy of the GIT, you can achieve this task. This strategy will replace the master branch entirely with the working branch.
Lets do this step by step:
Checkout the working branch (say working_branch)
git checkout working_branch
Merge with master with ours strategy
git merge -s ours master
You can add some comment to keep the track of what we are doing.
Now checkout the master branch
git checkout master
And finally merge your working branch with the master branch
git merge working_branch
Now your master branch has been replaced with the working branch, now you can push your master code to GIT.
git push origin master