Notification says I’m hacked then gives me an app

You haven't been hacked, but whatever website you visited is hoping you're gullible enough to believe you were and that you'll open your wallet to pay for service/tools/software, you don't need for a problem you don't have.

Ignore the message. Stop going to whatever website which was paid by scammers to try to get you scared enough to believe them and pay them.

Read this --> Recognize and avoid social engineering schemes including phishing messages, phony support calls, and other scams - Apple Support

You were not hacked, it is a scam message designed to get you to purchase unnecessary software or phish for personal information. Just ignore the pop-up, you are going to see many of these on the web.

The count down timer is there to give a sense of urgency and panic, another ploy to make you click on the link.

How would the software know when a hacker was going to shut down your phone?

Read more about it here -

Recognize and avoid social engineering schemes including phishing messages, phony support calls, and other scams - Apple Support

This isn't the first time a vendor has used scare tactics to drive people towards their app.

I'll be reporting this to the mods. With any luck, the app will be pulled and the developer's Apple account license revoked.

Re: “I was searching up something on safari and a notification popped up saying that my phone had been hacked and there is a hacker tracking my activity. It then took me to a white screen counting down the time I have left before my phone was shutdown or something like that.”

Scam!!!