Phone is not working Properly

@bobbysmith46124 just to expand on the excellent answer provide by my esteemed colleague @strongbow.

For now, you really want to stop continuing to try to charge, sync or otherwise use your phone. This potentially can make a bad situation worse.This may further damage your phone.

The next thing to do is to clean it. Disassemble your phone using these guides and teardown iPhone 12 Pro Max . You must remove all EMI shields off the boards. If you do not remove those, you might as well not do anything. After you removed those, clean the whole board, connectors and all with +90% isopropyl alcohol. Follow this guide, and even so it was written for an iPhone 3G all the points are still pertinent to your phone as well. While you clean your board, check for any obvious damage, like burned or missing components etc. Once it is properly cleaned, replace the battery. All these steps are to avoid delayed failure caused by corrosion. Best thing to do would be to clean it with an ultrasonic cleaner, but if you do not have access to one, this will at least help. Once all this is done, reassemble your phone and re-evaluate. Until it is cleaned, everything will only be a guess. It is possible that you have a bad LCD and replacing the display assembly may fix it. Even with all this, water damage has only a small chance to be fully repaired, but at least you can give it a try.