How do I sign out of a single Gmail account?

I want to sign out of a Gmail account on my laptop. On the Internet, I should just click on the picture at the top right and then click on unsubscribe, but then I can only unsubscribe from all accounts, but I only want to unsubscribe from one.

I do not know it either. But a friend did it for me through Teamview or something. There was something with "separate" or "separate". Then it worked.