What does ya te hey mean?

Yáʼátʼééh is used the same way "hello!" is used in English.

It literally means: it is good, well, fine, wonderful.

"shił yá'át'ééh" can mean "I like it". "nił yá'át'ééh"-- "you like it", "bił yá'át'ééh" -- he/she/it likes it.

It is not really pronounced " ya-ta-hey".

Navajo is a tonal language, there is high, low, rising and falling tone. The marks above the vowels here make it high tone. Sing the Word higher than your normal speaking voice.

I have attached a link of the Word being pronounced so you can try to say it correctly.

The mark between the two "a"s is a glottal stop consonant. We have it in English in "Uh'oh".

The t' is a sound we don't have. It is different than a t which they also have. It is a glottalized consonant. To say it you hold your breath in your throat and say t rather explosively.