The left key press will never get actioned, because you have it in an At beginning of scene condition. This will only action once, at the very start of the scene opening.
In both events you set SelectedAct to a value, then modify it. Setting the variable each time prevents it from continually increasing or decreasing.
Did you want the SelectedAct of 2 text objects? Or just 1?
Here’s a solution that will get you on the right path, but it’s assuming SelectedAct belongs to one text object: