Text sizing on slider

I’ve created some slides with 800px width and some text side the slide.

The text has 300px width and 250 height area, it shows great on the slide

But when browsing on a smartphone, the text is bigger than the slide conflicting with other widgets and sections of the page.

Is it possible to resize the text according to the (responsive) slider within the plugin?
Will editing CSS help?

I’m not really good with CSS on the first place ??

Thanks in advance ??

https://www.ads-software.com/plugins/master-slider/