We have this plant at my father house. The picture attached is the offspring of single plant we grow, it took 5 years to have this. I took the picture at the moment I replying this.

It is normal for the inner section losing leaves. Look at the picture, but this is if garderner trimmed the leaves. I am not sure if bonsai pruning style can improve the inner ramification.

He told me about this plant years ago, they need a lot of water. *Make sure not to pool the water, adjust the drainage to be slower.

*This what I understand from what he said.