Creating treadmill/spline with random spawning objects

Hello guys, let’s get straight to the point.

This is what I’m trying to make

I wan’t to make a simple line (wavy terrain) on which items will spawn. The items need to be fixed on the line, spawn on the right side, move to the left and disappear after meeting the collision box.

And this is what I’ve made so far.

I made a simple conveyor belt (highlighted box with an arrow) whose speed increases over time. Above the belt, there is a spline, which spawns random blocks, but I don’t like it and I will try to substitute it with different solution.

I can’t go further because I feel like I’m hitting a wall the more time I spend on it. So that’s why I’m asking You for help.

I don’t expect You to explain in details a solution, but to show me the right way to accomplish this. Links to tutorials are mostly appreciated.