Rebuild Existing POS application Change Work flow and with Strong database design and strong Performance

I want to redesign existing POS point of sale application feature and work fow there will be little change the rest will be same what i need technically strong application like current application is slow database design not good when scan it scan very slowly

i want application strong very fast even 200 thousand product also available in inventory when scan item should not affect
Module :
Inventory Management
Sales
Purchase
Expense
Accounting
Discount Management
Label Printing and Barcode
HRM
Report
Multi Warehouse and Multi Store System

Note : Company Only experience with Point of sale application should bid make bid with your demo link dont send me code canyon script link i check all point of sale application of code canyon so if you send online script i will know

i attached file for changes i need and i menion my existing pos application link also