How to make a Lego continuous conveyor belt
If you want the belts to operating in a single plane, you could try having an angled blockage across the corner which diverts the blocks onto the next belt, like this.



If you don't mind them going slightly up hill then all you need to do is make the one it is dropping off finish up high and have the next one be underneath it. In your diagram the dark green belt runs right into the wall, in my diagram below the dark greening finishes mid-air and the block and drop onto the cyan one.