i have a calendar virus on my iphone 6

That is a Rogue Calendar account. 

If you are using iOS 13 or earlier version (You appear to be using iOS 11) then Go to Settings ➔ Passwords & Accounts and under Accounts see if an unknown calendar account is listed. If it is then tap on it and then Delete account.

If you are using iOS 14 the Go to Settings ➔ Calendar ➔ Accounts and under Accounts see if an unknown calendar account is listed. If it is then tap on it and then Delete account.

Note that it is not a virus. It is something that got added to your calendar because you may have accepted an offer from a pop-up on a website unknowingly. Please be careful out there.

Axel F

 If running iOS 13 or earlier versions, check: Settings - Passwords & Accounts - Accounts - Any rogue entries here? If so, delete the rogue account. 

If running iOS 14, check: Settings - Calendar - Accounts - Any rogue entries here? If so, delete the rogue account.