You're partly right, but it's not that simple. There are many layers to this existence.
You can "see the future" in a lucid dream, and it will happen as you saw it. But, when you see the future in a lucid dream you actually have the chance to change it by reprogramming your dream!
We are living out predetermined scripts during the day, but we are creating the scripts during the night while we're sleeping, it's not set in stone since the Big Bang as you believe. Day time is for acting out and experiencing, night time is for "script writing", even though we normally forget what we were actually doing when we wake up. That's to make sure we focus on having the experience while awake.
We are actually "making shit up as we go" in this life, but not quite the way most people think.