Hi there,

you can increase the height of the textarea with 

textarea {
    height: 50px;
}

increase the height, in pixels, and add the code to customizer -> additional CSS

Hello,

if you increase the line's position 1 pixel less than the textarea height . So for example let's say you want the message area to be 250px height

textarea {
    height: 250px;
}

.message-box label.input_label {
    top: 249px;
}