remove site-title and site-description from mobile

I thought it at some point was like this, but I just recently saw, that my website does (again/still?) show site-title and site-description when being viewed from a mobile. Is there a way in Zakra customizer to change standard settings to make this happen? or do I need to add custom CSS?

I tried changing from

@media screen and (max-width: 480px){
	.site-branding {
			width: 30%;
	}
}

to

@media screen and (max-width: 480px){
	.site-branding {
			width: 30%;
	}
	 .site-title .site-description {
        display: none;
    }
}

but didn’t succeed. Can you please help?
best, Achim

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