hacked iphone

It's probably not hacked, there is usually other explanations to what happens.

Anyways, you can wipe everything on your phone and download all the software again from the internet if you want.

Restore your iPhone, iPad, or iPod to factory settings - Apple Support

But as I said, most likely your phone is not hacked, iPhone is a very closed ecosystem and there is no straightforward way for anyone to hack it. If weird stuff is happening its very likely another explanation

iPad and iPhone malware is fairly rare.

It’s much more common for users to get hacked.

What sort of misbehavior or unexpected behavior is arising?

An iPhone can not be hacked as long as it isn't jailbroken.

Why do you think your phone is hacked? If you describe what is wrong perhaps we can help you troubleshoot.

No not really.

The OS is really locked and you can only install stuff from the App Store.

I’m here assuming you’re not sharing an Apple ID.

If you are sharing an Apple ID, stop. Use Family Sharing.

Random videos? Any particular app? Check with the app vendor.

Open the App Store, search for the Readdle app, and then look on the Readdle app page for the support link, and follow that to the app vendor support info.