A B747 First Officer reported fire warning in cargo compartment and diversion to a nearby airport.

Narrative

Att FL320 system master warning FIRE MAIN DECK AFT annunciated. Notified ATC and descended to FL250 initially; QRH checklist initiated and diversion started to ZZZZ. Diversion decision made to ZZZZ as airport was CAVOK having just passed overhead within the past few minutes; having 2 suitable runways and familiar to the captain. PA was made; and supplementary crew members returned to flight deck to assist with diversion. All crewmembers donned oxygen masks and the airplane was depressurized. Vectors given to ILS-Z runway XX. Master fire warning reoccurred multiple times during descent and approach. Some communications issues occurred once oxygen masks were removed below 10;000 feet. Crewmembers were unable to reset the boom mic function despite multiple attempts. This led to delayed flap extension and hence once established on final approach @ approximately 600' due higher than normal speed a go-around was performed and the published missed approach followed.ATC vectors for return to runway XX; overweight landing from stable approach @ 306T. Normal touchdown rate of descent F30 A Brake 3. Stopped on runway near to intersection. No fire or smoke confirmed and taxied to parking bay with follow me car and fire services trailing in attendance.