I suppose while theoretically possible, it really isn't practical to write a modern web application in c++. Even if you did, you would either have to spend a ton of time writing it in c++ or end up with something that is the equivalent of a 20 year old web framework.

C++ is great for many things, but writing web applications isn't one of them. If you want a web app that is current, you'll need to write it in a modern framework.

I do Microsoft technologies, so I would write the web app and web service in .Net Core 2.x, but there are other languages that offer web frameworks, such java and python.

You need to read up on web application development because the subject is too broad for me to give you even a start of what it is all about.

For .NET Core 2.x web development, search bing or google for "how to write a web application in .net core 2". Plenty of info and tutorials out there. Btw, if you go this route, you'll want to use the lastest Visual Studio 2017 Community edition to develop with.