The first decision should be a mimicked Standard action, which means that the condition has always to result in true. You can use (I posted a screenshot)
IF 1 is equal to 1 or if you don't like numbers
IF me is equal to me
In your screenshot I see that you try to create something else? WHY????
Please, reproduce what I showed you many answers before!
And your last question, I have already answered as well: create a standard advanced action, that you trigger On Enter for the slide and that resets all your variables to 0:
Assign uv_volume with 0
.....