Tum hi Ho is a famous song of Bollywood.
It was one of the main themes of the India movie Aashiqui 2. (https://www.youtube.com/watch?v=IJq0yyWug1k)
Aashiqui 2 is a love story centering on the turbulent relationship between musicians Rahul and Arohi, a relationship which is affected by Rahul’s issues with alcohol abuse and temperament
The translation of the lyrics can be found here:
Here there is a basic transcription of the music score made by Krishnakumar Srinivasan