Problems with Overflows

Hi guys,
I’m struggling to create an overflow in my app. I have a few groups in a floating box, the main group height is 100% with allowing vertical scrolling when content overflows.
Inside I have a repeating group that is set to fit height to content and I would like to be able to scroll when the content overflows from bottom to top so people sees the last messages down close to the messaging box and they have to scroll up if they want to see the past messages. Does anyone here has an idea on how to achieve that?
Here is the link to the test page.

Thank you in advance,
A.