My phone black screen and cannot be charged.

@device_owner this “rear camera will fog up” and obviously this “a little water inside” would make me treat it as a water damaged phone.

For now 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 Samsung Galaxy S10 . You must remove all EMI shields from the circuit board. 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 a 3G all the points are still pertinent to your phone. While you clean your board, check for any obvious damage, like burned or missing components, corrosion on the board etc. When 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. Do not forget to replace the battery. This is a must and not an option. It will fail if you do not take care of it now. Once all this is done, reassemble your phone and reevaluate. Until it is cleaned, everything will only be a guess. Even with all this, water damage has only a small chance to be fully repaired, but at least you can give it a try. Change your cleaning habit and stay way from using “wet napkin” to clean your devices.

@device_owner now it could be time to check out the function of the board. You did get all the components on the board properly cleaned and you do have a new battery?

Start by following the flowchart

The PCB Layout will let you search for the components, like L8026, that need to be checked. Just use the search function of your PDF reader.