This is basic level programming, I doubt you will find anyone here on the forum to give you the answer but I can reveal the way.
Thinking about the construction of the Esp in C# the basic structure would be:
-Create overlay which goes above games window
-Get games base address
-Read the camera, all the entities, position, fov ...
-Convert the data read to a usable format through a W2S function.
-draw on the overlay using DirectX, OpenGL ...
Research about it and learn for yourself.
Remembering that creating Esp is easy. It is difficult to find a way to not be auto banned.