Renato, You have had your bonsai only two days and it is dropping leaves. It is likely stressed from the move - change of location.
You have a Fukien tea tree. Google it - learn all you can about this species. This forum has much info, and also see the companion forum on "indoor bonsai". Scroll back and you will find much discussion on Fukien. Give your tree the proper lighting required, temp, moisture (watering), HUMIDITY, air-circulation, and then fertilizing as needed. Bonsai soil and good drainage are important. If your pot has an attached saucer that traps water be sure to drain the water out or it will keep the soil too wet.
It is a tree and not a houseplant or decoration. As you learn about your particular tree you will then be able to care for it and keep it healthy and happy. For now don't panic - it needs time to readjust to the new home (and conditions) you provide for it.
ENJOY BONSAI !!!