Is hard resetting my iPhone 7 will erase all my pictures in my phone

Hard to tell what it is you want to do.

If you just want to restart the phone and it does not appear to be restarting properly, hold the power button and the volume-down button until the screen goes dark and then let go of the buttons.

If you want to restore the phone to like-new condition with all of the content and settings erased, then yes, it will erase your pictures, as well. You could store the pictures elsewhere before starting this process, or back up the phone to iTunes.

Here's how to erase it:

Connect the iPhone to a computer with the latest version of iTunes running. Hold down the power button and the home button while the screen goes dark, and then the Apple appears and disappears and then the iTunes logo appears. Once the iTunes logo is on the screen of the iPhone, you can let go of the buttons. (If this is an iPhone 7 or newer, you'll hold down the power button and the volume-down button instead.)

There is a prompt on the computer screen that says there is something wrong with the iPhone. Select Restore and follow the prompts. This will erase the iPhone, and you will lose all of your content and settings.

The iPhone will be ready when it says hello on the iPhone screen.

A hard reset will NOT erase ANY data.

Press both the on button on the side of your phone plus a volume button an d don’t release until you see the Apple logo.