Where to go out in Sofia ?

Hi everyone ! I am a student from Belgium and I'm coming on a trip to Sofia during next week. We are about 10 friends and we are looking for places tu go out. Every night club seems to open only on thursday-friday-saturday and we are coming from Sunday to Thursday.

Do you have any adress we could go to that would be open ? Maybe somewhere we can meet Bulgarian people (not the most touristic places).