Change Header Text and add Login Button

I’m having trouble working out how to do a couple of things on my site.

Firstly when users are logged in there’s a gray bar across the top of the page with a link to dashboard, add new post etc. and text in the far right saying Howdy, Rob (or whatever the user is called). I’d like to be able to change the text to say Hi instead of Howdy if possible but can’t find any options for it anywhere.

Secondly I’d like to add a login button similar to the one in the sidebar at the moment to just below the header. Can anyone help me achieve this, and in particular how to make it hide when the user is logged in?

My site is https://eucc.org.uk if anyone wants to know

Thanks