You can try adding this to the custom css for the theme in the admin panel. What is happening is when the virtual keyboard opens in mobile it causes the cursor to scroll up behind the toolbar. This is a discussed issue on mobile forums on the net. Landscape orientation doesn't appear to be possible since the keyboard takes up about 75% of the screen. There is just not enough room for both. The message element is provided by Oxwall, and is definitely not responsive. I have tried to at least size it to make it better.
.ow_chat_block form .ow_chat_mailchat_inputarea .jhtmlarea {
height: 100% !important;
}