Cell phone WiFi

[brucem]

I have recently bought a Moto G04 smart phone to replace my stolen dumb phone ( a Nokia 3310).  I have it connected to our Fritzbox router.  I now have my wife's phone book on my phone.  Some of the people I don't even know.  I would like to delete those that I don't want, but can I do this without deleting them from my wife's phone ( a move that could be fatal!)?  How do I do this?