First of all I’d like to thank u:)
The marble design :
First from acrylic u build the nail bed extension and than cover only the new nail bed with dark pink or transparent pink. After u find a fresh white powder and a black, u just put a little black in the white powder and than shuffle the 2 powders but carefully not fully just to see some black within the white. Than u build the whole free edge from it.
I also have a tutorial of the marble design on my Facebook page, u can check out :)