Eh...have to give landlord opportunity to fix and they have to fix within a certain time period from when you make the complaint. If it's an emergency item (those aren't btw), you can get fixed yourself and bill the landlord for it.
I'm not sure if you can negotiate a lower rent payment until problems are fixed or get reimbursed for the inconvenience, but you legally have to pay the rent or you risk breaking the lease (the broken shit doesn't break the lease unless they never fix). Real estate agents are generally pretty good about getting problems sorted if you stay on their backs. If they don't fix then you could go to VCAT and break the lease without penalty, getting bond and any pro-rata rent paid in advance back.
landlord has 14 days to attend to non urgent maintenance.. also you cant just fix urgent items and bill the landlord you have to notify the agent / landlord IF no action is taken in a reasonable time frame then you can do that but be careful its a minefield as if its deemed to be excessive or a problem the tenant was responsible for they get stuck with the bill.
best bet is submit maintenance request if no action in 14 days apply to vcat they most likely wont terminate the lease but they will give the agent power to use the rent to get items attended to in order of necessity if your really lucky they might let you out