Read the beginner's guide Chapter 13.2 "Program with 3 activities" to see how to communicate between separate activities. Also, you don't need StartActivity("Main") in the addperson activity; instead, use Activity.Finish.
To pass values between activities, you need to store the information in Sub Process_Globals. Unfortunately, you cannot put views there, so instead you need to put placeholders there and copy the information to the view in Sub Activity_Resume.
I have altered your code and placed comments where I changed things. Hopefully between the Beginner's Guide and my example you should be able to figure out what is done.