Unlimited text box in fillable form

Creating a fillable form. I want the text boxes to be unlimited. I know it starts as automatically, but when I type in the box and as it fills up, the text gets smaller instead of the box continuing to get larger. Is there a way to make the text stay the same size and have the box get larger? I have multiple fillable boxes on my sheet. (for reference, this is an employee performance review sheet, for the employee to fill out and answer questions.)