Hello,

Please add this code into your custom css box:

@media (max-width: 480px){
    .rev_slider_wrapper .rev_slider {
    height: 190px !important;
}}

to increase the slider height in order for the call to action button not be cropped.
See result screenshot.
As for the arrows they are responsive already, but if you wish to decrease their dimensions further then add this code (inside the media rule block above):

.tparrows {
    width: 40px !important;
    height: 40px !important;
}

and change the values to your wish.

Best regards!