how do i change the text under a navigation menu [closed]

I see two rather ‘quick’ ways of doing this: either you hide what appears to be the page title by css, or you edit the page template accordingly. Both should be done in a child theme.

Hiding the title with a few lines of css would probably be the quicker, but also a bit dirtier way to do this. For example:

.entry-title {
    display: none;
}

You’ll find an introduction to child themes here at wordpress.org.