Why do i have these childish behaviors at 90?

You choose: Starting point: what are you calling childish, what about it bothers you? Where do you do it? When? How does it serve you? Next point: what do you want from yourself instead, why do you want it? Next point: mentally rehearse new behaviors in the presence of old triggers until they become familiar to you. Your behavior isn't happening to you, but through you. Identify and choose new behaviors.

Kudos to you: As long as your behaviors do not cause harm to yourself or others, i think you should keep right on being young at heart.I bet you're a fun grandparent / great-grandparent!