how do I keep my iPhone safe from malware or

You do not need to worry about Viruses or Malware being installed on your iPhone. It is simply not possible unless you have jailbroken your device. You do need to make sure your Apple account is kept safe by not providing anyone your Apple ID/Password and not following for any phishing attempts.

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

Never give your phone to anyone to use

Never divulge your Apple ID or Apple ID Password

Never click on a link in any message or email unless you are certain that the sender and link are legitimate

Ignore and delete any messages that claim that viruses or malware have been detected on your phone

Ignore and delete any messages claiming that you need a VPN

There's probably more, but this would be a good start.

There are no known viruses or malware that can affect an iPhone.