Prestashop customizations

I need 2 changes in my Prestashop: 1. I need to import customers database from an Excel page to my Prestashop. The format is totally different from the one of Prestashop and you have to edit the document in way it be accepted by Prestashop. I attach the file so you can check if you can. 2. The field 'Select a quantity' should increase the number of pieces in multiples of the minimum quantity for that product. E.g.= The product named Blue pen has the minimum quantity of 8 pieces. If the customer click on the up arrow for increasing the quantity he will see 16, then 24, 32, 40 etc. and he can't have the chance to order a different quantity such as 10 pieces, for example. This criterion should work in every order review page, in the cart and in the main order page, so wherever you have the possibility to change the quantity of the products.