Hi there! I've started playing this game last week. Well, I want to keep my town clean that's why I place lots of trash bin in the area but everytime I open the game the next day, the trash bins are empty but lots of cans and other trash everywere. There comes a time that the trash bins are full but I don't know how to empty it.

You don't have to empty them. They'll empty on their own. Placement of trash bins is an art as much as it's a science.