Welcome to the forums. Unfortunately your question is a little vague and may not be answerable without more info.
Was the app specifically named "phone manager?"
Which phone make and model?
What did this app do, or what are you trying to accomplish? (This would help us suggest alternatives if needed.)
You will need to register an account here to reply, but doing so and giving us more info will help us give the best advice. This link will walk you through it.
https://forums.androidcentral.com/sh...d.php?t=409154
