[c#] - fixing multithreadings by add Asynchronous Programming with Async and Await

Hello, I've a c# program than send multi threading webclient requests using a rotation proxies, but the program only can handle 15 threads otherwise it going to freeze! I want to fix that by adding async or await so i can use more threads if that logic works! Note: I need somebody to be able to connect to my team viewer to fix the issue. for learning propose. thank you, regards.