First off, your first event is unconditional. So it gets run all the time. Your first event should have an At the beginning of the scene condition.
Secondly, if you create a tween for the same thing (in this case opacity changes), delete the previous one before creating a new one.
Thirdly, you are changing the scene as soon as the left mouse button is released. Do it once teh fade has occurred. I’d suggest implementing something like :
