ADD A STRIPE PAYMENT SYSTEM TO OUR EXISTING APP - INSTALL NEW API AND PAYMENT GATEWAY XAMARIN APP

We have an existing ANDROID app on Google Play. The CC Payment System that came with the app does not work, so we need to have someone who is an expert in STRIPE or any payment gateway system that can take credit cards in our app. WE CAN NOT use Braintree / PayPal, so it has to be STRIPE or any other system that maybe you are experienced with. This is for selling memberships and merchandise. WE ARE ON A BUDGET and need your best price because we have a lot of work to be done, which we can give you if you can get a payment system added to our app. This can be a long term relationship if the price is right. But if we can't start taking payments for memberships, then we have no money.