h4 not applied [orbilan]

Hi

I need to apply h4 formatting to the headings as seen on this screenshot, which is taken from this page.

On desktop the h4 will be rendered correctly:
46 px

but the spacing is weird on tablet!

I have created a Global Style "flexi-h4" in order to style this, but whatever I enter for margin- or padding-bottom does not apply.

Also weird, that a value of 92px is displayed as greyed-out value.

I am unable to use apply the h4-formatting via Customizer > Typography, or via Global Styles.
I feel super lost, nothing works, I have checked all the settings (desktop, tablet, mobile) everywhere it may have been tweaked :(

Can you please help me with this?

Credentials below.

Thank you in advance and kind regards,
Sascha