I've been trying to find the name of this movie for so long. When I was younger, there was a movie I always rented and loved, and I just can't remember the name. It was like, a princess kidnapped by these trolls or something? And I remember in the beginning this boy walking up a mountain or something and singing. Could you help me with the title?

Its kind of like that in the movie "the secret garden"

Maybe that's it?

I refer you to this thread, which I believe has your answer:

https://www.askmehelpdesk.com/movies/troll-cartoon-movie-cant-remember-title-104064.html?highlight=troll