Your mother's great great uncle is your great great great uncle
Your Uncle.
I call my mother mom
great-great uncle
great great great
Your grandfather's uncle is your great great uncle. Your grandfather's brother would be your great uncle
Your mother's mother is your grandmother.
Your great uncle.
He would be your great great uncle, but you could call him whatever endearing name you both prefer. my great grandfathers brother or my great uncle
Your mother's father's uncle is your mother's great uncle and your great great uncle.
Your mother's uncle is your great uncle.
Your relation to your mums uncle is GREAT uncle. You're welcome! 
He is your uncle, in most families he would be Uncle (Jack, Fred or what ever his first name is).