grammar structures of english

hi every one , how's everything today ?
hoping the best things for you all
a few days ago i was studying a book , and there was a grammar structure in ''it'' , in accordance with this grammar rule , when we are talking to some body we can say ; oh man you are older than me , but in writing mode we can't use ''me'' after 'than' , in contrary we shall use ''i'' after 'than' .
also i hear some teachers say ; what kind of human you are ?
and some other teachers say ; which kind of human you are ?
and that's why i`m wondered , i don`t know how to put it
in accordance with a grammar rule i studied a few days ago , in this sentence we shall use which , since 'which' denotes quantity and when we wanna choose one out of a definite number , we use which
what`s your opinion ?

This is good work. I enjoy to reading it.

I wish you the success!