Alert pop up "your phone has been hacked"

I clicked on an add for shopping, and an alert said that my "phone has been hacked, 17% or something has been taken." Then said I had a minute or something to download an app called "online barrier" like a VPN? Is this all a scam, even the app? I was scared so I downloaded the app and tried it. I looked up similar questions and people said it was a scam! How can I stop it…

it keep popping on my screen