How can I prevent someone from mirroring my iPhone?

No one is mirroring your phone. Users who share an Apple ID are able to make changed to their account that will be reflected on each phone. Change your Apple ID Password to prevent that from happening.

Change your Apple ID password - Apple Support

You can view other devices that are signed into your account by going to Settings > [name on top], and scrolling to the bottom to review the devices.

You can also use Safety Check to make sure you are not sharing information with others.

How Safety Check on iPhone works to keep you safe - Apple Support

If you are seeing this behavior while using an app such as FaceBook or Instagram, then it is that account that has been compromised.

tairahafrank wrote:

My neighbors has hacked my phone and is changing my settings and doing weird things while i’m on my phone. how do i stop it from happening

No, they haven't. That's simply not possible.