I am a retired high school math teacher. I have a degree in pure mathematics (1982). My dissertation was about Semigroups of Linear Operators in Banach Spaces.
I quitted further specialization because I liked very much teaching; anyway I love to practice math at any level.
I like very much this site, mathexchange, often it's too difficult for me; nevertheless it's always stimulating for me to (re)learn math topics.