Changes Required in Existing PHP POS (Point of Sale Application) and make it Progressive Web App

How my application work: First I enter product then product available in system you cant sale yet since you did not make quantity adjustment which means item received in your store from supplier when item received from supplier you either do purchase or to assign product quantity to warehouse we make quantity adjustment when we do quantity adjustment it means I assign product quantity to warehouse now to distribute the product from warehouse to store we make quantity adjustment store after making quantity adjustment store item goes to store then shop can sale item this is the procedure you received item you send store item and you sell item from store When entering product there is 4 type of product standard combo digital and services when I buy the application from code canyon service type product also need quantity adjustment to sale it since application work this way right now below changes I need00 Changes I need 1. When I click on product type services it should be sale without any quantity adjustment means unlimited product you will add two button in product type one service another restaurant both will function same services and restaurant same function just to give a extra button when people click one product type is services or restaurant the product will be sale unlimited they don’t need to make quantity adjustment since service type product there is no quantity its just service so when click product type as services or other menu I said system then select warehouse and select store will be visible if default did not select any option then the item can be sale from all store and all warehouse if select particular warehouse and can be sale to all store under this warehouse and if select under that warehouse particular store then can be sale on that specific store 2. One changes I made before from actual application if item is out of quantity then not to visible in POS screen my previous developer change it from coding and make it invisible if item is out of stock I want on off feature for this in setting so I can control it from setting instead of editing script this i need because application has default feature also in setting sale item even out of stock if u turn on then u can sale item even item is not in stock I need to make this control in setting 3. Make the application Progressive means right now application work if u have internet if internet disconnect middle of transaction u can’t sale I want to make it progressive even no internet connection still transaction will happen and when internet return all data will synch to server automatic need to make sure no error happen sometime in offline from store may be 10 counter will do transaction so when internet come back when all 10 counter synch data must make sure no data lose or any error happen calculation should be accurate so application should work from cache even internet disconnect 4. Integrating New Interface i have the design in html and css Demo Username: temp Password : Temp1234 [login to view URL]