Text cut of on Mobile

When i view the top headline and the centered textblock on Mobile, it cuts of one piece and it just stops resizing at one point. Can anyone help me with that

i already tried to add this this (no results):
function.php:

add_theme_support(‘avia_template_builder_custom_css’);

stylsheet.css:

@media only screen and (max-width: 479px) { .start-titel { background: none !important; } }

@media only screen and (max-width: 479px) { .start-text { background: none !important; } }