I'm hearing namastee a lot these days. It's quite stylish. The origin of the Hindi greeting has a spiritual significance, but it's a common greeting in India, and doesn't guarantee the person who utters it isn't going to cut your throat two seconds later.
But that's neither here nor there. What Fio wants to do is teach you how to pronounce namastee so she doesn't grit her teeth and cut your throat herself.
Listen up, people! It's not nah-mah-stay, but nuh-mus-stay! The "a's" are schwas and rhyme with "huh." They are Hindi's "short a's." (The "long a" in Hindi rhymes with "la" and is indicated by doubling the letter: "aa.")
The reason for the two "e's" on the end of namastee is that it indicates the vowel is long and should rhyme with "stay". (The short "e" in Hindi is the same "e" as in "led.")
Oh, and the "t" is soft, like in Spanish.