Mail on my iPhone

This is not a chat service. This is a user to user technical support forum and Apple does not participate here. You need to type out a question describing your problem and any troubleshooting steps you have taken to fix it, and wait for one of the volunteer users to read it and one to answer it.

Slow down and give someone a chance to read and respond to this.

Swipe all the way to the left and bring up the App Library. From there, find the Mail app and long press and hold and drag it back to the home screen.