Veryfaying current app functionalty and fix problems exist

I got this app which it sppose to be for final delivery before posting it up to google play, and i am the owner see a lot of problems in the app, but the devloper claim nothing wrong with it, due to this conflict we will spend another 10 years he would say thire are no issues to be fixed and i would say a lot of problems exist, Due to that i am looking for real expert in the app development who can spot where are the problems and fix it for me he can be part of the sission to discuss the issue of problems and how the current developer solve it but it isn't practical way for me The app main functionalty is about connecting sellers with buyers who has same intrests only and send notification either way based on interest first second on the demographical postion the app also generate discount cobouns but in the current desgne there is no way show how the buyer claim his product or service from seller, if any developer has ready made script and like to use it insted of my current app i also will come that but it must be delivered in the next 10 days, the app support arabic and english the app use paypal and paytab payments gate ways i like to paypal to be set for me as owner to use split payment feature and also any person can pay any person feature using paypal in easy way Please i don't like to waste my time and yours don't bid before reading and understanding the requerments, thanks