Is there a possibility to change the wording of the menuitems?

Hello!
I use this plugin with my menu:

User
Log In | Log Out

Means when the user is logged in, the name is shown and as a submenu Log Out is shown and when the user is logged out, there is only show Log In. Now I’d like to change the wordings of the different menu items.

1. User is showns with the fullname. I’d like only to see the firstname
2. Log In => Login
3. Log Out => Logout

Is this possible?
Thanks and greetings from Austria!