how do i get the 6th crystel

Defeat the boss of the Dark World's sixth dungeon, which is in the southwest corner of the world map.

I have been trying to figure out how to get in there.

u need to lift up a dark stone in the very corner i think

once you get the flute and the emblem on the mountain(read walkthroughs for that)use the flute to fly to the 6th place(if that's not it it's the one in the bottom left corner)pick up the dark stones(you need to have gotten the 4th dungeons treasure)one of them will have a warp thing.walk on it and you will be in the dark world.go up a bit and you will see a symbol on the ground of the emblem you got on the mountain.use it.you'll figure it out from there.

how can i get into the swamp of evil?

It was just stated how to get it, don't be come a nusence and ask something that's already been explained. In case you didn't know, "The Swamp of Evil" is the sixth dungeon.

Eeeeeh, I'm trying to defeat Ganon inside the Piramide
Can somebody tell me the way how?

Slash away at him until the lanterns go out. Light them and hit him with your sword to stun him. Shoot him with a silver arrow and repeat the process until he dies.