Title will not change

Hello,

I am really new to this, so please excuse me for being so basic.

I am trying to change the title of my site from “Diner”, which is the theme I am using, to something else, but it will not change. I have changed it in general settings/site title, but my home page still says diner. When I scroll the mouse over diner, the pop up bubble says my tagline, but it is not visible.

Any ideas?