WouldBe
Dislicksick
The cistern is that black box behind your bog. Mine sticks sometimes so the valve doesn't close and it keeps emptying while trying to fill. Usually if you press the flush again it sorts it out.
The flush mechanism is inside the cistern so you need to get in there as you have disconnected the flush mechanism.
As for the leak it may be coming from the pipe that links the cistern to the bog. Usually there is a large plastic nut under the cistern. Check if it's tight. The other end of the pipe has a rubber seal on it to make a seal with the bog. Make sure it's pushed into the bog fully.
The flush mechanism is inside the cistern so you need to get in there as you have disconnected the flush mechanism.
As for the leak it may be coming from the pipe that links the cistern to the bog. Usually there is a large plastic nut under the cistern. Check if it's tight. The other end of the pipe has a rubber seal on it to make a seal with the bog. Make sure it's pushed into the bog fully.