The rear brakes you seem to describe are known as drum brakes and the part you are trying to remove is the drum.
I mean no offence but if you neither have the tools or experience of working at these type of brakes I would respectfully suggest you seek advice either from a professional outlet or a friend who has experience.
Brakes are a vital safety component of your car and like best friends you miss them most when they ain't there. Plus you have a duty of care to your passengers and other road users.
i was NOT going to remove the brake, i just needed to know how much was left on them, i do know some stuff about how to fix a car, but i only know what i have seen other do. i was in a bit of a hurry before so i couldn't think of the word ''drum'', but yes you are right in thinking its the drum brakes. i wanted to get the drum off (yes with handbrake off and just in gear) and check how much brake was left on it and give the drum a good clean (with sand paper) as when i was hammering at it, loads of black crap was coming out of it.
on every other car i have done this with i have never had to take out the center nut (where the Greece goes, just get a hammer, bang it towards you slightly and pull it and it comes off.
and Thank You BobbyDog i didn't know the nut needed replacing afterwards, the nut and the little dish thing around it seems pretty dry, so i think it also need greasing, was told to buy copper grease by my granddad.
I NEED TO check how much brake is left on it has when i am breaking it sometimes sounds like it is grinding at the back (like metal against metal) i do have some tools, but i am jobless and only on job seekers, sop i cant afford many tools, i have a socket set, but the biggest socket i have it just a little bit small lol.
when ever i do ANY work on the car i always give it a test drive BY MYSELF 1st, drive it to a quiet road, do emergency brake and stuff and give it a good run so i can check for any vibration and stuff in the steering.