If you have fans and portals enabled, you should be able to find a stronger sword and then, with that, double jump boots, and then you should be able to find the four magic gems that will unlock the door to the final level.
Yes, I agree that this game can be very confusing. It's surprisingly hard to make a metroidvania that feels intuitive in the sense that the player always has an idea where to go next (I think this is also true for many commercial metroidvanias, I have stopped playing so many of them because I have got completely stuck!)