This is only the relevant method for opening shops.

ShopGUI.java

    private void openShop(Player p, String shopName) {
        System.out.println("Opened shop!");

        Merchant merchant = Bukkit.createMerchant(ChatColor.RED + shopStorage.getShopOwner(shopName) + ChatColor.RED + "'s §a§b§c§d§e§f§cShop");
        List<MerchantRecipe> recipes = new ArrayList<>();

        shopStorage.getShopItems(shopName).forEach((item, price) -> recipes.add(utility.createShopItem(serializer.stringToItem(item.toString()), ((String) price))));

        merchant.setRecipes(recipes);
        p.openMerchant(merchant, true);
    }