Missing packages and open mail is a constant situation in my building. I've spoken to the postal manager from my zone,but problem has continued to persist.what steps do I need to take to have this issue dealt with?

From my experience your going to have to catch the person and it report to the police. They are not going to do much for you. Your better off sending putting your packages on hold and leave at post office to pick up. In order to do this you need to set up an account with them.

move to a better area or stop using USPS