I can't get it done and can't find anything about it, either I'm blind or I don't know xD either

I would like that one size 4 + 5 and
Size 6 + 7 can buy. Can someone help me integrate this into the GUIShop?

Thank you and everyone stays healthy :)

I believe there is a permission feature of GUI shop where players can buy a permission. That's how you'll want to go about this. Refer to the GUI shop docs for examples.