How do I display long text part after part ?

In my game, I ve a dialog display system showing the text in a box that contains 3 lines. Text to display maybe more and I'd like display part after part when space bar is pressed.

I've made a test offsetting the text when bar is presse but it doesn't work (overflow text is not displayed).

I'm not looking for a visual scroll system, just a system showing the first part of the text, then erase text box and fill it with the rest of the text.

Here's a simple design

and here my attempt code

https://www.dropbox.com/scl/fi/onn4rqfe4mepzc87ckp0n/ScrollText.c3p?rlkey=r6cn2nzifjvr05ok5ea9h2hvv&dl=0

Sentence after sentence dialogue system: dropbox.com/s/xmn99g03i2jliv1/dialogue_panel.capx