If the narcissist is clever, they will also initially show some interest in your life. Don't worry, this soon passes.
Because to the narcissist, you are just a mirror.
The narcissist wants you to show them good things about themself. They will spend increasing amounts of time getting you to talk about them, doing things for them, them them them.
If you give in, the narcissist swells up like a tick, feeding on your compliments and attention. They stop talking about your things at all, or at most listen in bored silence when you need to talk about a you thing. They barely acknowledge when you've done something they've asked you to do.
And you shrivel up inside, until you feel hollow and empty and sad. You have to detach the narcissist before they explode from the life they are sucking out of you, leaving you just an empty shell.
You cannot have a relationship with a narcissist because they will only ever be emotionally involved with themself.