When My boss asks "Como estas? I reply : "Estoy muy muy feliz" Does it make sense in spanish? Or What is a better/polite way to say "I am fine"?
Estoy muy, muy feliz
is fine if you are talking with a close friend and want to share your great vital situation.
But if you want to share something more polite in a random conversation with somebody not being that close, you better use other expressions such as:
[Muy] bien, gracias.
Estoy bien, gracias.
Note that these kind of questions are normally meant to be used as a salutation, normally people don't expect but a polite reply asking for them. So you normally add a
¿Y tú/usted? after it.
Funny addendum: In Argentina you can also hear a response like:
escoge: ¿bien o te cuento?, meaning: I am saying I am fine based on the fact you are just asking this for courtesy; but if you really care, I can tell you :)
"Estoy muy muy feliz" does make sense. But I don't think that is the answer you want to tell to your boss. I am going to be concise with this answer: Think about when someone asks you "How are you?" you rarely say "I'am happy." People usually reply "I'm fine, thank you" or "I am good/great"
If you reply "Estoy muy feliz" is not wrong. It depends on the context.