Hello ,hope are you well there
i have 7 years of experience in mobile (android / ios ) app development.
I have seen your BUY and SELL app requirement and I have developed many application like your requirement.
We do BUY and SELL app like for merchant and user where merchant post there products according to category with multiple images , price , description etc .In user side user can see the products see all images , add to cart , order history , filter items , purchase items, like, share products etc.
Also provide admin panel for manage category , manage users , manage merchant etc.
Yes we do gps location also so user can search by location and nearby also
I will complete your project in less time or in minimum amount with 6 months of support.
Send me message for more discussion
waiting for your positive response
Thanks