charging problem and lag on iphone 12 pro max

Hello gigii1910,

We understand that you’re experiencing slowness and charging issues with your iPhone. Is that correct? If so, we recommend the steps in the links below

If your iPhone or iPod touch won't charge - Apple Support

If your device charges slowly or won’t charge

Follow these steps and try again after each:

1) Check your charging cable and USB adapter for signs of damage, like breakage or bent prongs. Don't use damaged accessories.

2) Use a wall power outlet and check for firm connections between your charging cable, USB wall adapter, and wall outlet or AC power cable, or try a different outlet. 

3) Remove any debris from the charging port on the bottom of your device, then firmly plug your charging cable into your device. If the charging port is damaged, your device probably needs service.

4) Let your device charge for a half hour.

5) If your device is still unresponsive, force restart your device: 

*iPhone 8 or later and iPhone SE (2nd generation): Press and quickly release the volume up button. Press and quickly release the volume down button. Press and hold the side button until the Apple logo appears.

*iPhone 7, iPhone 7 Plus, and iPod touch (7th generation): Press and hold both the side (or top) button and the volume down button until the Apple logo appears. 

*iPhone 6s or earlier, iPhone SE (1st generation), and iPod touch (6th generation) or earlier: Press and hold both the side (or top) button and the Home button until the Apple logo appears.

6) Let your device charge for another half hour.

About iOS or iPadOS performance on your iPhone, iPad, or iPod touch - Apple Support

Check your network conditions

Many apps on your device require an internet connection for their content and other functionality. If the network that you're connected to is congested—for example, at an event with many people using the same network—apps might take a while to open or display their content. Your device can also seem slow as it repeatedly reconnects to new cell towers when you're in a moving vehicle.

Even if your device indicates a strong signal, you might need to wait, try again in a different location, or use available Wi-Fi. If you continue to experience issues with cellular data speed, availability, or performance in multiple locations, contact your carrier.

We recommend the steps above because they can help troubleshoot the slowness and charging issues you're experiencing on your iPhone.

Post back if you still have problems after working through the steps in the links above. 

Thanks for using the Apple Support Communities.

Cheers!