Hello @MDVL! Welcome to the Typeform Community! 

Unfortunately, it's not possible to edit the size of a specific part of your text. Our designs are responsive because we want to make sure the forms will be adaptable and readable on any kind of device, that's why this is not an option now. 

 However, there're two workarounds I can think off:

1. You can select a font from our library that is tinier and remove Bold text if you're using it.
    
2. You can make the text smaller in a text editor app, take a screenshot and upload it as an image. This will allow you to make the fonts as small as you want them to. Even better, create a .png file with a transparent background in an image editor app of the text so you can insert it in front of any background.

Other than that, the only option to edit the font size is clicking in Design > My theme > Click in the three dots beside it > Edit. Over there, you can choose between small, medium, and large for the 'Welcome Screen & Endings' and for the 'Questions'. Take a look at this article from our Help Center if you wish to know more about it.

Let me know if any of these workarounds would be able to help you!  Wishing you a great day!