This is an awesome idea that I think you could turn into a really unique game
Suggestion for the future: Instead of giving the player one instance of the object that they have to pick up and fly around the truck, maybe give the player a piece of paper with a blueprint of the object and some measurements. Like a drawing of the sphere that says something like “1/3 of actual size”. If you give the player a simple tool like a ruler, you could add a lot more depth to the gameplay.
Also, I feel like making the player fill the truck up is just tedious and unnecessary. Maybe it’s just because the current character controller doesn’t work well for the task. It might be better if you have each object spawn on top of the truck and the player just moves it along the X and Z axis and just chooses where it’ll drop.