Battery

Read the Service and Parts History section detailed in this link --> About genuine iPhone batteries - Apple Support

Your iPhone must be updated to iOS 15.2 or higher.

You can schedule an appointment at your Apple Store Genius Bar for a battery replacement. Apple used to publish the prices, but now has this link, which you can enter your details to get the price. The iPhone X will either be $49 or $69.

See this --> iPhone Service & Repair - Apple Support