Is this Safari pop up a virus?

This looks more like a scam:

Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support

They removed your screenshot but from what I remember when it was showing, you were very low on battery power and you had Low Power Mode turned on. Charge your phone and turn off low power mode and your phone should run faster.

Imliptontea wrote:

Yea I had low battery but it was lagging only when that page was open I have no clue why, after I closed it I had no problem. So there is no way there is a virus, I’m just kinda worried on why it made safari laggy

You're worried because some advertisers used words that scare you to put an idea in your head.

You're in fear for the security of your device.

But consider how you got hacked here, and not your device.

Scammers know this too—that fear can motivate us—and they know which words we fear, and they know that we ourselves are much easier to hack than are our devices.

Close the webpage, get on with what you want and need to be doing, and spend a little time to learn more about how these scams work.

if you're concerned about device security (who isn't?), enable two-factor on your Apple ID if not already, set up your recovery contact and/or trusted telephone numbers, configure and use iCloud backups or regular local backups, pick unique and robust passwords, keep your devices patched to current, and work through the list of Apple security recommendations available for you.

Scammers and advertisers won't tell you about any of that work of course, as they only want to sell you some miracle cure, err, miracle app, or they want to convince you to install the malware or the sketchy app yourself.

Advertisers and politicians routinely use fear too—words like "hacker" and "virus", here—because those work. They get us to do things against our own best interests. Here? Review and upgrade your own security, backups, passwords, and all.

Generally speaking yes, but if you used the backup to restore from, any damaged data might still be part of the backup.

It’s not a virus. It’s just a scam popup.

That's a sketchy popup advertisement that—best case—is selling what is probably a sketchy VPN add-on app that you don't need or want. Ignore it.