Textfield will not expand vertically, as form filler fills out a text field, it will automatically advance to the right to allow the user to continue typing.
If you have a 'Multilines' textfield, as the form filler reaches the right margin of the input box/area, it will wrap to the next line, and if it goes down beyond the input box, it will automatically scroll down and you will see the vertical scroll bar.
it will not expand to display the entire input text when text go beyond the predefined width/height of the form field. When you save the response as PDF in View Responses tab, then the saved response-PDF-form does 'expand to fit" the entire text input. Also, when you are editing the form field in Design tab, you can always select the field and resize it (click on the resize handle and drag)
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