Problem with the form - the message can be moved sideways after expanding

Hi all. As in the title, if someone wanted to enlarge the message, I would like it to be possible to scroll down instead of sideways. In short, there is a button to enlarge the message, I want it to only be possible to scroll down. It's my first time making a form and I can't quite get it done.

mypen: https://codepen.io/Bartomiej-/pen/MWLBpjO