I keep getting a popup after going on thiscrush.com. It says i have 4 virus from adult websites. Do i actually have viruses or is it a scam?

It tells me to buy an app on google play even though i have an iphone

It is a scam.
Any popup tells you that your device have a virus is a scam, and if you install the antivirus as they had told you to, you will end up with fake antivirus software that may mess up your device.
Download and install an antivirus from a reputable website to protect your phone.