i'm lost.. pls help

You need to hit the switch to raise the gate then use the new power to run and slip underneath it, then go from there.

Is that level 8 with Dante or Lucia? With Dante, you just need to defeat the boss, if you want help with beating him I can give advice, he is one of the harder bosses. If you mean Lucia, you're probably getting used to being underwater. From the start go up until you escape the water. There is a large odd-shaped stone pillar at one end of the room. Examine it by pressing O I think, and it should give you some text, and start shooting fireballs periodically. They deal absolutely tiny damage if they hit you so don't worry, but you have to hit 3 of them so that they fly back into the statue (it doesn't matter which way you're facing when you hit, they always fly back at the statue if you hit them at all). 3 hits will break the statue and flood the room, so check along the ceiling for a hole you can swim up now. There are other puzzles in the level but the only 1 you have to do is quite simple, you just keep breaking the spheres that come out of the ground until you smash 8, and the other gets you a Heart, and involves breaking a bunch of mummy-coffin looking things which come back to life, so you kinda need to weaken them all first, and then break them all close-together. After that's the level's boss, hope I was helpful .