Please help us help you and fill where relevant:
Your LimeSurvey version: 3.24.3
Survey theme/template: corporate one
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Hi everyone,

I would like to increase the font of text inputs in questions of type "Short free text" and, at the same time, the height of the text box. I'm aware this is more of a css question than a LimeSurvey one, but I decided to ask it here since I was not able to find the name of the css class I should overwrite, nor with which property (font-size I guess?).
Could someone help me? Or tell me where to get these pieces of information? I'm a beginner...
For info my custom survey theme is based on Fruity.
Thank you very much!

Hi,

Or tell me where to get these pieces of information?

Always investigate your page with the webdevelopment tool of your browser (F12).
Here im Firefox you see this
 

Hovering the desired object shows the settings.
Obviously interesting are the "height" and the "font-size".
You can edit the values here to see the effect.
 

Now you may enter the new values into your question like
Or you add it to your "custom.css" with an additional class like
.bigtext input.form-control {
...

Then you can call this behaviour by entering "bigtext" into the "css classes" of your question.

Joffm​​​​​​​

Perfect! Thank you so much! Knowing this gives me MUCH more freedom and control over the appearance of my survey! I changed what I wanted to modify, and many other things.
Have a nice afternoon!