Purple And Blue

Hello everyone,
I'm not at this Point, where you should wear this ancient helmet and go under the water to this middlespike.
But when in trying to enter it, it tell me: "magical powers asseble as you as you try and enter, maing you unable to Approach the cave"
Now i can't enter it and the quest book doesnt update, when im speaking again to the starting villager, he tells me to do what he told me

If you know what i have to do, i would be very thakful if you have me some hints or tell me what to do, or what im doing wrong

 

What does your book say? where your helmet (if you have it)

 

I have it and i'm wearing it, while trying to enter this middle spike from under the lake

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but I'm always getting tepeported back to the cave entrance with the red text i just wrote on my post