are iphones free from viruses or do I need an antivirus software

You don't need any Anti-virus for your iPhone. Just make sure you update your ios software whenever there is any new updates available. Also take a backup of your data on a computer and icloud whenever possible and always before updating ios.

Those Anti-virus are not made by Apple, they are all made by third party developers. Anyone can publish their application on appstore by following app store guidelines. Apple always focus on their security part and comes up with security updates.

iPhones have very strong protection built-in - you don't need antivirus software: it would do more harm than good.

Because the manufacturers make money by scaring people into thinking that they need these apps. It's the modern equivalent of the snake-oil salesman.

You are most welcome. 😊