Replace Faucet Seat

I have an 2 Handle Shower faucet. I am familar with replacing the washer. Actually I did it before.
Now I managed to fix the leak faucet again last Saturday.
I change the washer of hotwater faucet. When I test it, still leak, even I make it very tightly.
Later I feel the faucet Seat may not good. I checked it. It is really bad with break edge.


So, just a small part of faucet. I replaced it and all done. The faucet can be turned off easily.
I am not handyman. I got help from the building caretaker, Bill. Thank you bill for you help and advice.