Sharing iPhone account

You don’t!

Immediately stop sharing an Apple ID, for this and many additional reasons.

The person creating the new ID must thoroughly cleanse her/his Apple devices as follows:

What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch - Apple Support

Then “move in” to the like-new device (software-wise).

If you wish:

Set up Family Sharing - Apple Support

Apple IDs are personal; they shouldn’t be shared any more than you would share a toothbrush. If you share an Apple ID with someone else many bad things will happen. Each user should have their own Apple ID, then you can create Family Sharing→ What is Family Sharing? - Apple Support. That way you can share what you want to share and not share what you don’t want to share.

It is OK to share an Apple ID among devices used by one person, such as an iPhone, an iPad and a Mac; in fact, it is a very useful thing to do. But not between devices used by different people.

Here is Apple’s FAQ: https://appleid.apple.com/faq/#!&page=faq. See the 4th bullet item.