One of my good friends

Today I went to eat lunch with Mr Guna. He is my good friend .He always take me to lunch . I am grateful to him .
Because I dont want to go for lunch alone. He must understand my feeling . He also give me good advice and hints for work almost every time.
For example He teach me how to behave as a coach and how to manage the sports club and so on .
So I want to call him teacher.
Acutually I and he is same place of work . He is very good trainer especially teach boxing .
I respect him not only as a trainer but also as a man .