How do I show/ mirror my iPhone 12 Pro Max in Sony Bravia TV?

Does your Sony TV support AirPlay directly? If not, you still have two options available for your iPhone:

1. Via an Apple TV.
2. Via an HDMI cable with something like this cable: Apple Lightning AV Digital Adapter

Ref:

• Use AirPlay to stream video or mirror your device’s screen - Apple Support
• How to Connect iPhone or iPad to Your TV: HDMI Cable or AirPlay with Apple TV - iPhoneLife

The TV needs to support AirPlay 2. Check the specifications for the TV. Otherwise the only thing you can do is use an adapter and HDMI cable.