I can't remember the name of a certain movie I watched when I was a little kid. I remember there was a princess who sang a lot and there were I believe maybe trolls that opened up a magic door for her to get around. And there was a warrior guy that was trying to save her because someone kidnapped her father and was keeping her prisoner. I know the trees are possesed as well. It was made I think in the late 80's or 90's. If you could help I would appreciate it so much!

It's pretty far fetched, but maybe "Little Nemo: Adventures in Slumberland (http://imdb.com/title/tt0104740/)" (1989) everything you mentioned is in that movie except there are slight differences to each. So it may not be what your looking for.

Previously asked and answered:

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