creating a new custom table

I need a new custom table, I already have done something, I have a page “Ordini” (I can open it from my left menu admin) but it’s empty https://ibb.co/jvLmZkF, it should be with many fields like my subscribers table: https://ibb.co/1Rpx1gh . I should have a button at the top bar in my admin “New Order” (putting just the custom button and the link is easy), when I click on “New Order I see a page with all my custom fields. Some fields will have a selector so that I can import data from subscribers or come directly from subscribers page, more or less like that https://ibb.co/sty3C9S

The page I need help with: [log in to see the link]