Your red Agaloanema looks great and the only thing that needs adjusting is your expectations.
The leaves and the stems naturally orient themselves to get maximum light exposure. If the light was coming from directly overhead rather than the sides, then the stems would be more upright. But I think yours looks great just the way it is now growing.
In time, the stems will get longer and some will start to lean way over the side of the pot. Those can then be shortened by pruning them back. New growth will emerge subsequently after pruning. Selective pruning is the way that you can manage the overall shape and size of your plant. Otherwise, keep up the good work!