italy permesso di soggiorno and visa

Hi people,i have question to ask.I am a currently erasmus student in Italy(Bari).Normally i am here for one semester and because of it my visa( type d ) going to expire march 03 but my school give me second semester too so now i have to extend my visa some how.I applied to parmesso di soggiorno but post office gave me appointment date of parmesso di soggiorno on 23 of march so i guess i have to live here without visa atleast 20 days... I went to police for this and they say you already make appointment so you can come at 23.But ı don't have ıtalian she don't have english and the police center was very crowded so i am not sure any all of this.I have a letter that is showed i applied to parmesso di soggiorno but i kindly ask may i go my country and come back with my passaport and that letter or is there a any way to add more day to my visa ? what should i have to do .

New topic
connection to localhost:9312 failed (errno=111, msg=Connection refused)