Oh i see.
Normally in games with a limited text box size, like a dialogue box, they show a bit of text then the player clicks and it deletes the old text and shows some more.
An alternative is to have a scroll box.
Use "force own texture" and "destination out" to hide text outside of the scroll box area.
But if you want to change the text size to always fit i guess you'd have to set the text, then get the text width, see if its greater than the window size, if it is then resize the text and check it again until it fits. You could do this in a loop normally so it appeared to happen instantly however its a bit tricky with the text object as it doest update until the next game loop, hence the wait 0.1 action.