but the tree still loses its new leaves..
What can I do?
Please help me
Unless you are keeping it in an unshaded southern window you should get some form of supplemental lighting.
The soil is very heavy & organic, meaning water retentive. Eventually it will need to be re-potted into a free draining medium. In the meantime utilize the chopstick method to determine when to water.
Learn about it here: https://www.helpfulgardener.com/forum/vi ... =36&t=1479
Learn about proper bonsai soil here: https://www.helpfulgardener.com/forum/vi ... =36&t=3422
Keeping trees/shrubs inside is a skill unto itself and not all will be doable. Your tree will really do better outside (weather permitting) if you are able and willing to do so.