How does saving work???

[Nvjds]

Im playing ocarina of time, and I just beat the deku tree and got into the hyrule castle, but every damn time i open OoT it takes me back to the very beginning of the deku tree. I always press save befofe closing, i even wait like a minute just to be sure that it saved, but it always goes to the deku tree. Why wont it save?!?! Also on the save slots the first slot seems to be where i was in the castle but i have no idea how to play that save. Please help!