Hello,

Please try adding the following Custom CSS in the Custom CSS for Mobile area under Theme Settings >> Custom CSS.

.page-title .entry-title {
    font-size: 50px;
}

This will change the page title size on mobile.

If you are trying to ask anything else then please provide with some relevant screenshots of the specific area where the title is enabled because currently, the page titles are disabled on your mobile.

Regards.
Xtemos Studios.