Looking to build an app

Hello
Well im buying coins from sweat coin in algeria thro messenger and im have cusstomers so i want an auto matic app
People will send their coin and i pay them in algerian currency ( dinar )
So i want to make it east for me , they will send from hhe app and upload picture i csn verify and pay them it show paid..
And i will work ln the app more later for the best offer and asap
Thank you