How can I unregister a Git VCS root?

Question

I want to use a java project from GitHub. I would like to write and compile it using Idea Community Edition 14.0 on my machine and execute Pull / Push etc. To git. To synchronize the project with Git, I followed these steps:

• Idea - VCS → Checkout from version control - GitHub (main branch loaded)
• Idea - project_name → Git → Repository → Branches → my_branch_name → Place an order as a new local branch

After these steps, it was possible to work with java classes in the my_branch_name project. But after a while, the following message appeared: "The my_branch_name directory is under Git, but is not registered in the settings." I clicked "Add root" :). And now I can’t add new Java classes, I don’t see one open class from another, I can’t execute the main procedure - there is a message “The process has completed with exit code 1” (but it was started successfully earlier).

I understand that I added a new root? How can I fix it now? Please help, thanks in advance