Delete custom profils field (registration page)

Hello,
How can i delete profile fields “YTCName” and “Twitch Channel”.
I trie to rename first “YTCName” for “Steam Profile”. But the field “YTCName” is respawning on my registration page, and yet, i have 3 customs fields and i can not delete them. How can i delete this 3 custom profil field on the registration page ?

Screenshot link: https://vgy.me/bNHmrS.png

(sorry for my bad english)
Thanks