How to switch back to 'master' with git?

According to the Git Cheatsheet you have to create the branch first

git branch [branchName]

and then

git checkout [branchName]

You need to checkout the branch:

git checkout master

or

git checkout main

See the Git cheat sheets for more information.

Edit: Please note that git does not manage empty directories, so you'll have to manage them yourself. If your directory is empty, just remove it directly.