Hello, I am late to bid as i was going through your website.I have checked your website and your interesting requirements carefully. You wants me to come up with idea to increase your business with the mobile app.
Yes, let me tell my idea for you. As you are thinking to build something for your customers to connect between them also to the customer service. Its great. Another think we can do is we can use APIs from your website and show item in the app so users can also buy from the app. And also can make a bot for the user. When user ask any question the bot will automatically answer. And a user can also buy a item by just writing a message. For promotion the app can use some features like Most selling item of the day. Item of the month something like those.
In terms of sharing with friends, we can make a feature to share in social media by one click with a funny message and link. And also can offer user's upon share by a referral program to increase you sell.
First of all this is not a copy paste bid. I can discuss more about it. And can develop the app with those. Contact me.
I am able to start working on your project from today, And I can design the app using Material design that your end-user's will like. I am new here, but have over 2 years industry level job experience. I will deliver you the product with 2 month's free support.
Thanks.
Mujahid