Malpighia Glabra

This is a Barbados cherry bonsai that I saw at an exhibition in Putrajaya, KL. I have a few of this in my backyard but they seem to grow rather slowly and after two years of growing them on the ground, I still can not do any work on them. please do advise if you have any tips especially on the best soil mixture and other things that can make the trees thrive . Thanks.

Zaratul,

how about a few images of your efforts?

Soil - what do you use as soil ?
Looking to read your response.
Khaimraj