Subscriptions are alive as long as the page they’ve been created in is in view, on exiting or navigating away to another page you must unsubscribe to avoid issues like memory leaks.
A Subscription is an object that represents a disposable resource, usually the execution of an Observable. A Subscription has one important method,
unsubscribe, that takes no argument and just disposes the resource held by the subscription.
What you need to work with is Behaviorsubject.
Go through the previous links I shared above, they lay out the road map you need to achieve 