Q:

"Te tengo que decir adiós" o "tengo a decir adiós"

¡Buenas, amigos!  Yo tengo una pregunta, yo escucho una canción, y algunas palabras son:

"Te tengo que decir adios"

¿Cómo?  Al decir "I have to say goodbye" en español, ¿por qué no dice "yo tengo a decir adios"?  Porque dice "te" antes de "tengo"?  ¿Y por qué dice "que" y no "a" antes de "decir"?
Gracias, y lo siento por mi español, yo sé que no es bueno pero ¡¡estoy aprendiendo!!

A:

Though "I have to say goodbye" could be translated merely as "Tengo que decir adiós", "Te tengo que decir adiós" is literally "I have to say goodbye to you". Te here is just a use of the dative case, that's why it's easier to understand it if you look at the sentence as "I have to say goodbye to you", you can see now the noun which the goodbye is being addressed to.
As for why tengo que is used is because "have to" implies obligation or necessity, which in Spanish needs the conjunction que, just like in English it needs to in order to become a modal verb (often considered as such, not sure if it indeed is one or just simply the verb like in Spanish).

