Problem with Our Android App - Help Required

Hi,
We have an android App for our e-commerce business.
while using the app as a guest, it is working perfectly.
But after registering on the app, many of the product categories shows "Zero Product"
Can some one help us in solving the problem?
Link to the App: Dehaat.Store : गाँव का शॉपिंग मॉल nline Shopping (On google Play Store)
Before giving us any random quotes, we request you to first analyse the problems in the app's user interface and then offer us your best quotes and time lines with the solution.
Reply awaited

Thanks for the reply.
We are Not sure whether it is with Android or website problem.
The Freelancing person who developed the app has shifted abroad for his job.
Earlier when we had lesser number of products, there was no problem in the app. But as the number of products have grown up, this problem has started.
That is why, we asked to check the app, if some one can understand the problem and offer us the solution, time frame and pricing, we can initiate the contact.

Dear James,

App connects to the same database for both guest and registered users.

Hi James,
Can you solve it? if yes, How much would you charge for it and how long would you take to resolve it?