Virus on calendar

It basically means that you have exposed your address somewhere.

1. Go to your iCloud Calendar page via a desktop browser.
2. Click the gear icon in the lower-left corner, click Preferences > Advanced.
3. In the Invitations section, change the option from In-App Notifications to Email to iCloud Address.

You can also tap on this Event and report it Junk. This will remove the event and won’t notify the sender.

iPhones cannot be hacked or infected with Virus / Malware / Spyware by merely clicking on a link in Safari, unless you have intentionally downloaded spurious softwares or unauthorised apps directly from internet and installed on your iPhone or/and have Jail Broken.

You need to look at the way you share your sensitive and valuable informations of your device with your friends and family members.

See: Spam in my calendar - Apple Community

I got the same things too but I really don know how to delete it

This is not a virus. This is basically spam.

What calendar are you using? Google? iCloud?