Need a secured website and Mobile App for selling products online

I would like to build a website to sell my FMCG products online. I have a huge SKU with a huge demand and I am unable to manage my inventory and missing many orders. Need help in sorting these issues. I would first like to see a proposal before shortlisting a Freelancer on how you can help me in solving my business problem, while technologies will be used, will a technology solution given by you is Secure and can I have cloud solution and how can this be integrated with my existing accounting software. I also need some insights and recommendations based on data. Only serious candidates needs to apply. Contact me for more details