fantasybox. How to dynamically resize an iframe?

Question

css

Hello!
The point is the following. There is iframe. It contains a feedback form with a text field. If you manually change the size of the text field, then everything below is hidden outside the frame. There should be no scroll bar. How to win it, tell me please ?? I don’t even know what to use, or css or what js code is needed.
Original view of the form:

After changing the dimensions of the text field: