I still couldn't get stamp on my passport for my application. Is that a problem if I have to show my passport to police? Because my visa is already expired.

Submitting application in person preceded by registration of the appointment is the best way to get the stamp in your passport. If application was sent via traditional post you will need to wait for the letter/call from our office in order to fullfill formal requirments and get the stamp. When meeting the police in the time between visa expiration and obtaing stamp in the passport, you can only tell the case number, when application was sent to our office and what kind of application it was. Police and Border Guard will be able to get confirmation of given information.