my iphone is expose to virus

No it cannot be, there are no iPhone viruses.

Wherever the warning is coming from it is a hoax or scam.

Check out your calendars

In Calendar app, tap on Calendars and uncheck the ones you don’t recognise .

Then  Settings > Calendar > Accounts > Subscribed Calendars, look for the problem calendar and delete it.

https://support.apple.com/en-us/HT211076

When a website asks to send you notifications, special offers etc always say NO.