Block is over extending in Mobile view

Site URL: https://www.onyxhive.com.au

Hey guys,

The hero image purple text animation is over extending in mobile view. Sometimes the purple text animation in mobile view appears on the third line, my friend tried it and it was fine on hers. But on my android phone through the 'internet' and 'chrome' apps, they over extend. Please see screenshot.

How can I fix this so the box resizes to mobile view?

Edit: I half fixed it with code but the block is still over extending and leaving a black bar on the right

#block-yui_3_17_2_1_1620650758501_2648
{
  width: 94%;
  height: auto;
}

Try adding to Design > Custom CSS

@media screen and (max-width:640px) {
h1.sentence {
    overflow: hidden;
}
}