Microsoft .NET Framework 2 and aspx file editing for Paypal API and Sandbox -- 2

1. I need the Paypal IPN listener code added to the [login to view URL] file for my website uclaim.com. Paypal started requiring this a year or so back and without it, Paypal sends ipn's up to 20 times to my Access database, clogging up my database. And they threaten to turn off the ipns. Here is the Paypal instruction page: [login to view URL] 2. Paypal Developer - I need someone who understands Paypal Developer tools and Sandbox. I hired a developer to test out the Paypal payment process for [login to view URL] and set up ssl certificates. He used the sandbox to make some sample purchases on 9-4-2019. Ever since then, I have had various problems, such as paypal not calculating and showing sale prices on the payment page. The developer took my money, which I paid in advance, and has not responded to my emails in a year. I am wondering if he made some changes in a sandbox account that disrupted and disabled the normal payment process? I saw some email accounts in the sandbox that are unknown to me. It appears there is a switch to toggle off the sandbox and go live, but it does not seem to work for me. 3. Here are the other problems that may or may not resolve themselves after the listener code is added: 1. No internet connection message after the customer clicks the Verify Purchase button in the Register box, after payment was already made to PayPal. 2. I am not getting email notifications when a customer clicks the Purchase Online button in the Register box. 3. The product sale price is not showing up on the Paypal payment page. Only the regular price shows up. Help me with this, and there will be a lot more work for you. Thanks