Well, there are several ready-made frameworks available in the market that turns your online website into a feature-rich mobile app. I have also tried this for my website and I am completely satisfied. You don't need to write code every time to manage the functionality from back-end. The simple back-end functionality of this ready-made framework fascinates me the most. So, I would suggest you this solution.

Please check it out:
WooCommerce Mobile App Builder