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I need some help from anybody with coding/html experience

Hey my name is sander and i got a couple of questions, it has to do with copying a website and using it as my own but theres also a app that generates a random link from the site like www.blabla.com/secret/12312o3jaksldja something like that,

i want to make this aswell, would like to copy the site and modify it to my own liking.
Sorry my english is not the best but i hope you get what i mean and if u are interested in helping me out would love to hear from you.