Why aren't my texts getting smaller with the slider? / Everything about font sizes
Defaultly your text's size is based on the font size option at the Design tab of your layer's settings:
which would make your font smaller with the same pace, as your slider is getting smaller. For example your slider's width is 1000px, your font's size is 36px, then you look at the smaller version of your slider, when it has 500px width, and your font will have half it's original size too, 18px.
If your text doesn't behave like that, check out these settings:
This option makes your text to always have the given font size, so in this case your font won't get smaller or bigger, it will always stay in my example 36px.
Minimum font sizes
These values will limit down the minimum values your font sizes can be. For example if on an 1000px wide slider I have a text with 8px font size, and I make the slider half it's size: 500px, the font will have half it's size as well: 4px, but if I make the slider smaller, like 250px, the font size will still stay 4px, so it will never go smaller, than 4px.
Font size modifier
This setting can increase/decrease your font's size in the specific device views, where you are currently editing. For example I have 36px font size on Desktop and my slider's width is 1000px. I will make my slider smaller, 500px wide, where I see the Table view, and my font would have 18px size, but I choose to change it's size to 150% with the font size modifier, which will make this text 27px big on the 500px Tablet view. But it's not a fix size, so on Tablet view 450px, your font's size would go smaller to 36px*450px/1000px*150% = 24.3px.
If you are not sure about what Desktop, Tablet and Mobile views are, check out this video.
Custom CSS codes
Inside the "more" options of the Font and Style settings you can find their managers, which have Extra CSS options. If you put a font-size css code there, it will overwrite our css codes:
CSS code of the theme or a plugin
If you only see, that your font size behaves incorrectly in the frontend of your website, but not in the backend preview, then your theme or one of your plugins are modifying our code by using too strong css codes. You can see a video here, or a text documentation here to see, how you can inspect your text to see, where does the wrong css code coming from. You should remove or modify that css code to not be as strong, as it is currently. You can find a documentation here about css code priorities, which could help you make your code strong, but not as strong, that it would overwrite every font. Or this documentation could help to make that code to only apply to certain parts of your website, and not to the part, where you put our slider.