thank you for your help.
Unfortunately I can't see how to solve my problem with these infos.
The problem is the "Classic Custom Headline" at the top of the page I provided via SecureNote.
I can't see, where I could make the headline shown in a smaller size at certain viewports.
The calc() solution shown in 1.) needs a field for the font-size, wich isn't there at this element, right?
The bas font-size solution in 2.) will not work, because the genereal font size is perfectly OK, only the h1 / h1 headlines are to big in the smartphone-viewport.
The solution in 3.) is about very long textes - for me it's only one word, that isn't that long: "Landwirtschaft" - i think, this should be shown correctly without any tricks or hacks.
The reason, why I buy a theme like "X" is that I don't want to change css etc. in standard-situations. The theme's job is, to do that for me to save my time and my clients money
So any hint, how to get my h1 / h2 headlines smaller on smartphones, without changing base font size and without adapting every element, that contains a headline?