Enhancement to an OpenCart Website

I have an open cart website with Webkul Multi-vendor marketplace extension installed with the hyperlocal extension that calculates the shipping cost according to the distance between seller and customer what I really need is this : 1- As an admin : I should be able to add/update/disable (manually or with excel sheet) the Country name which in turn has many Cities and the City has many Districts . In each Country I should be able to add Cities manually or via excel sheet (same for a City with Districts ) . 2- As a seller : I should be able to set my "selling locations" by choosing a Country from a drop down list and a City from drop down list as well , knowing that Selecting the District/Districts shall depend on the choosing of Country and City. (of course will depend on the previously added data by the Admin. ). 2-1 For Shipping prices : Aa s a seller , he should be able to set his shipping price depending on District/Districts , as well , he should be able to set shipping price to a Single District or a group of Districts. 3- As a registered customer : 3-1 He should be able to add his address and specify the Country, City and District from a drop down list. 3-2 He should be able to see products from those sellers who sell in his location (address) . Also (customer default address should be set as his location by default). In addition , products price should be shown in the store as (original price + shipping price) depending on customer location. 3-3 When he wishes to change his location, a drop down list shows his addresses from the address book. 3-4 When he changes his location , a Warning should appear "these (products) not sold in the new location, ok to remove from the cart", ok, update cart products prices (product price + new shipping price) , He can only see products from those sellers who sell in his New location. 3-5 His shipping address in check out page should be the same as the location used in ordering the products. when he changes the shipping location ??, a warning should appear "these (products) cannot be shipped to this location , click ok to remove them from the cart ", ok, remove products if exists and update products prices (product price + new shipping price). 3-6 low cost products should be shown at the top of the store according to the customer location. 3-7 As an Anonymous user , He is required to enter his location , so he can view the store products accordingly.